diff --git a/build.gradle.kts b/build.gradle.kts
index 9b2fb99..9922be4 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -90,7 +90,11 @@ tasks.withType<JavaCompile> {
 }
 
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions.jvmTarget = "11"
+    kotlinOptions {
+        jvmTarget = "11"
+        useIR = true
+        freeCompilerArgs = freeCompilerArgs + "-Xopt-in=kotlin.contracts.ExperimentalContracts"
+    }
 }
 
 tasks.dokkaHtml {
diff --git a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/RestException.kt b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/RestException.kt
index 1679f96..137afb9 100644
--- a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/RestException.kt
+++ b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/RestException.kt
@@ -13,12 +13,9 @@ import org.springframework.web.bind.annotation.ExceptionHandler
 import org.springframework.web.context.request.WebRequest
 import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler
 
-abstract class RestException(val httpStatus: HttpStatus) : RuntimeException() {
-    abstract val exceptionMessage: String
+abstract class RestException(val exceptionMessage: String, val httpStatus: HttpStatus) : RuntimeException(exceptionMessage) {
     abstract fun buildBody(): RestExceptionBody
 
-    override val message: String by lazy { exceptionMessage }
-
     open inner class RestExceptionBody(val status: Int = httpStatus.value(), @JsonProperty("message") val message: String = exceptionMessage)
 }
 
diff --git a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityAlreadyExistsException.kt b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityAlreadyExistsException.kt
index 042a9e0..26232c5 100644
--- a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityAlreadyExistsException.kt
+++ b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityAlreadyExistsException.kt
@@ -5,15 +5,32 @@ import dev.fyloz.trial.colorrecipesexplorer.model.Model
 import org.springframework.http.HttpStatus
 import org.springframework.web.bind.annotation.ResponseStatus
 
-class EntityAlreadyExistsException(modelType: Class<out Model>, val identifierType: IdentifierType, val identifierName: String?, val requestedId: Any) : ModelException(modelType) {
-    constructor(modelType: Class<out Model>, identifierType: IdentifierType, requestedId: Any) : this(modelType, identifierType, identifierType.name, requestedId)
-    constructor(exception: EntityAlreadyExistsException) : this(exception.type, exception.identifierType, exception.identifierName, exception.requestedId)
+class EntityAlreadyExistsException(
+    modelType: Class<out Model>,
+    val identifierType: IdentifierType,
+    val identifierName: String?,
+    val requestedId: Any
+) : ModelException(modelType) {
+    constructor(modelType: Class<out Model>, identifierType: IdentifierType, requestedId: Any) : this(
+        modelType,
+        identifierType,
+        identifierType.name,
+        requestedId
+    )
+
+    constructor(exception: EntityAlreadyExistsException) : this(
+        exception.type,
+        exception.identifierType,
+        exception.identifierName,
+        exception.requestedId
+    )
 }
 
 @ResponseStatus(HttpStatus.CONFLICT)
-class EntityAlreadyExistsRestException(val value: Any) : RestException(HttpStatus.CONFLICT) {
-    override val exceptionMessage: String = "An entity with the given identifier already exists"
+class EntityAlreadyExistsRestException(val value: Any) :
+    RestException("An entity with the given identifier already exists", HttpStatus.CONFLICT) {
 
+    @Suppress("unused")
     override fun buildBody(): RestExceptionBody = object : RestExceptionBody() {
         val id = value
     }
diff --git a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityNotFoundException.kt b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityNotFoundException.kt
index fe499fd..e40eb45 100644
--- a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityNotFoundException.kt
+++ b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/exception/model/EntityNotFoundException.kt
@@ -5,14 +5,17 @@ import dev.fyloz.trial.colorrecipesexplorer.model.Model
 import org.springframework.http.HttpStatus
 import org.springframework.web.bind.annotation.ResponseStatus
 
-class EntityNotFoundException(modelType: Class<out Model>, val identifierType: IdentifierType, val identifierName: String, val requestedId: Any) : ModelException(modelType) {
-    constructor(modelType: Class<out Model>, identifierType: IdentifierType, requestedId: Any) : this(modelType, identifierType, identifierType.name, requestedId)
-}
+class EntityNotFoundException(
+    modelType: Class<out Model>,
+    val identifierType: IdentifierType,
+    val requestedId: Any
+) : ModelException(modelType)
 
 @ResponseStatus(HttpStatus.NOT_FOUND)
-class EntityNotFoundRestException(val value: Any) : RestException(HttpStatus.NOT_FOUND) {
-    override val exceptionMessage: String = "An entity could not be found with the given identifier"
+class EntityNotFoundRestException(val value: Any) :
+    RestException("An entity could not be found with the given identifier", HttpStatus.NOT_FOUND) {
 
+    @Suppress("unused")
     override fun buildBody(): RestExceptionBody = object : RestExceptionBody() {
         val id = value
     }
diff --git a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/service/model/MixTypeJavaService.java b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/service/model/MixTypeJavaService.java
index 7a5e050..92b72ef 100644
--- a/src/main/java/dev/fyloz/trial/colorrecipesexplorer/service/model/MixTypeJavaService.java
+++ b/src/main/java/dev/fyloz/trial/colorrecipesexplorer/service/model/MixTypeJavaService.java
@@ -66,7 +66,7 @@ public class MixTypeJavaService extends AbstractJavaService<MixType, MixTypeRepo
     public MixType getByMaterial(Material material) {
         Optional<MixType> found = findOptional(repository.findByMaterial(material));
         if (found.isEmpty())
-            throw new EntityNotFoundException(type, ModelException.IdentifierType.OTHER, MixTypeKt.IDENTIFIER_MATERIAL_NAME, material);
+            throw new EntityNotFoundException(type, ModelException.IdentifierType.OTHER, material);
 
         return found.get();
     }
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/ColorRecipesExplorerApplication.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/ColorRecipesExplorerApplication.kt
index 15b6483..4828d02 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/ColorRecipesExplorerApplication.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/ColorRecipesExplorerApplication.kt
@@ -2,20 +2,15 @@ package dev.fyloz.trial.colorrecipesexplorer
 
 import dev.fyloz.trial.colorrecipesexplorer.config.properties.CREProperties
 import dev.fyloz.trial.colorrecipesexplorer.config.properties.MaterialTypeProperties
-import org.slf4j.Logger
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration
-import org.springframework.boot.context.properties.ConfigurationProperties
 import org.springframework.boot.context.properties.EnableConfigurationProperties
-import org.springframework.boot.jdbc.DataSourceBuilder
 import org.springframework.boot.runApplication
-import org.springframework.context.annotation.Bean
-import javax.sql.DataSource
 
 @SpringBootApplication(exclude = [LiquibaseAutoConfiguration::class])
 @EnableConfigurationProperties(MaterialTypeProperties::class, CREProperties::class, DatabaseUpdaterProperties::class)
 class ColorRecipesExplorerApplication
 
-fun main(args: Array<String>) {
+fun main() {
     runApplication<ColorRecipesExplorerApplication>()
 }
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/config/WebSecurityConfig.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/config/WebSecurityConfig.kt
index 7f3e210..9863b35 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/config/WebSecurityConfig.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/config/WebSecurityConfig.kt
@@ -189,9 +189,9 @@ const val defaultGroupCookieName = "Default-Group"
 val blacklistedJwtTokens = mutableListOf<String>()
 
 class JwtAuthenticationFilter(
-    val authManager: AuthenticationManager,
-    val employeeService: EmployeeService,
-    val securityConfigurationProperties: SecurityConfigurationProperties
+    private val authManager: AuthenticationManager,
+    private val employeeService: EmployeeService,
+    private val securityConfigurationProperties: SecurityConfigurationProperties
 ) : UsernamePasswordAuthenticationFilter() {
     private var debugMode = false
 
@@ -238,8 +238,8 @@ class JwtAuthenticationFilter(
 }
 
 class JwtAuthorizationFilter(
-    val userDetailsService: EmployeeUserDetailsServiceImpl,
-    val securityConfigurationProperties: SecurityConfigurationProperties,
+    private val userDetailsService: EmployeeUserDetailsServiceImpl,
+    private val securityConfigurationProperties: SecurityConfigurationProperties,
     authenticationManager: AuthenticationManager
 ) : BasicAuthenticationFilter(authenticationManager) {
     override fun doFilterInternal(request: HttpServletRequest, response: HttpServletResponse, chain: FilterChain) {
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/AccountModel.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/AccountModel.kt
index b54a862..d00cd6b 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/AccountModel.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/AccountModel.kt
@@ -2,6 +2,7 @@ package dev.fyloz.trial.colorrecipesexplorer.model
 
 import com.fasterxml.jackson.annotation.JsonIgnore
 import com.fasterxml.jackson.annotation.JsonProperty
+import dev.fyloz.trial.colorrecipesexplorer.model.validation.NullOrNotBlank
 import org.hibernate.annotations.Fetch
 import org.hibernate.annotations.FetchMode
 import org.springframework.security.core.GrantedAuthority
@@ -109,18 +110,15 @@ open class EmployeeUpdateDto(
     @field:NotNull(message = EMPLOYEE_ID_NULL_MESSAGE)
     val id: Long,
 
-    @field:NotBlank(message = EMPLOYEE_FIRST_NAME_EMPTY_MESSAGE)
-    val firstName: String = "",
+    @field:NullOrNotBlank(message = EMPLOYEE_FIRST_NAME_EMPTY_MESSAGE)
+    val firstName: String?,
 
-    @field:NotBlank(message = EMPLOYEE_LAST_NAME_EMPTY_MESSAGE)
-    val lastName: String = "",
+    @field:NullOrNotBlank(message = EMPLOYEE_LAST_NAME_EMPTY_MESSAGE)
+    val lastName: String?,
 
     @Enumerated(EnumType.STRING)
-    val permissions: Set<EmployeePermission> = mutableSetOf()
-) : EntityDto<Employee> {
-    override fun toEntity(): Employee =
-        Employee(id, firstName, lastName, permissions = permissions.toMutableSet())
-}
+    val permissions: Set<EmployeePermission>?
+) : EntityDto<Employee>
 
 
 private const val GROUP_ID_NULL_MESSAGE = "Un identifiant est requis"
@@ -148,6 +146,7 @@ data class EmployeeGroup(
     @JsonIgnore
     val employees: MutableSet<Employee> = mutableSetOf()
 ) : NamedModel {
+    @JsonProperty("employeeCount")
     fun getEmployeeCount() = employees.size
 
     override fun equals(other: Any?): Boolean = other is EmployeeGroup && id == other.id && name == other.name
@@ -313,16 +312,6 @@ fun employee(
     lastLoginTime
 ).apply(op)
 
-fun employee(
-    employee: Employee,
-    newId: Long? = null
-) = with(employee) {
-    Employee(
-        newId
-            ?: id, firstName, lastName, password, isDefaultGroupUser, isSystemUser, group, permissions, lastLoginTime
-    )
-}
-
 fun employeeSaveDto(
     passwordEncoder: PasswordEncoder = BCryptPasswordEncoder(),
     id: Long = 0L,
@@ -350,12 +339,6 @@ fun employeeGroup(
     op: EmployeeGroup.() -> Unit = {}
 ) = EmployeeGroup(id, name, permissions, employees).apply(op)
 
-fun employeeGroup(
-    employeeGroup: EmployeeGroup,
-    newId: Long? = null,
-    newName: String? = null
-) = with(employeeGroup) { EmployeeGroup(newId ?: id, newName ?: name, permissions, employees) }
-
 fun employeeGroupSaveDto(
     name: String = "name",
     permissions: MutableSet<EmployeePermission> = mutableSetOf(),
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Material.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Material.kt
index a32183e..bfcd908 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Material.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Material.kt
@@ -9,7 +9,6 @@ import javax.persistence.*
 import javax.validation.constraints.Min
 import javax.validation.constraints.NotBlank
 import javax.validation.constraints.NotNull
-import javax.validation.constraints.Size
 
 private const val MATERIAL_ID_NULL_MESSAGE = "Un identifiant est requis"
 private const val MATERIAL_NAME_NULL_MESSAGE = "Un nom est requis"
@@ -98,6 +97,7 @@ data class InventoryMaterial(
     @NotNull val lowQuantity: Boolean = false
 )
 
+@Suppress("unused")
 fun Material.toInventoryMaterial(minimumQuantity: Float): InventoryMaterial {
     Assert.notNull(id, "Cannot convert a material without id to an inventory material")
     Assert.notNull(name, "Cannot convert a material without name to an inventory material")
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Model.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Model.kt
index 47795c7..825ad2b 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Model.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Model.kt
@@ -11,7 +11,7 @@ interface NamedModel : Model {
 
 interface EntityDto<out E> {
     /** Converts the dto to an actual entity. */
-    fun toEntity(): E
+    fun toEntity(): E {
+        throw UnsupportedOperationException()
+    }
 }
-
-fun Collection<Model>.sortedById(): Collection<Model> = this.sortedBy { it.id }
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Recipe.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Recipe.kt
index 353d1e9..4b904c1 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Recipe.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/Recipe.kt
@@ -50,6 +50,19 @@ data class Recipe(
     @OneToMany(cascade = [CascadeType.ALL], mappedBy = "recipe")
     var steps: MutableCollection<RecipeStep>
 ) : Model {
+    constructor() : this(
+        null,
+        "name",
+        "description",
+        0,
+        null,
+        "remark",
+        "note",
+        company(),
+        mutableListOf(),
+        mutableListOf()
+    )
+
     constructor(
         id: Long,
         name: String,
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/RecipeStep.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/RecipeStep.kt
index 393fb21..80ccd59 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/RecipeStep.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/RecipeStep.kt
@@ -1,10 +1,8 @@
 package dev.fyloz.trial.colorrecipesexplorer.model
 
 import com.fasterxml.jackson.annotation.JsonIgnore
-import dev.fyloz.trial.colorrecipesexplorer.model.validation.NullOrNotBlank
 import java.util.*
 import javax.persistence.*
-import javax.validation.constraints.NotNull
 
 @Entity
 @Table(name = "recipe_step")
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrNotBlank.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrNotBlank.kt
index 3610ad5..ef262c6 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrNotBlank.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrNotBlank.kt
@@ -3,7 +3,6 @@ package dev.fyloz.trial.colorrecipesexplorer.model.validation
 import javax.validation.Constraint
 import javax.validation.ConstraintValidator
 import javax.validation.ConstraintValidatorContext
-import javax.validation.Payload
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
 import kotlin.reflect.KClass
@@ -15,8 +14,7 @@ private const val MESSAGE = "must be null or not blank"
 @Constraint(validatedBy = [NullOrNotBlankValidator::class])
 annotation class NullOrNotBlank(
     val message: String = MESSAGE,
-    val groups: Array<KClass<*>> = [],
-    val payload: Array<KClass<out Payload>> = []
+    val groups: Array<KClass<*>> = []
 )
 
 class NullOrNotBlankValidator : ConstraintValidator<NullOrNotBlank, String> {
@@ -42,5 +40,4 @@ fun isNotNullAndNotBlank(value: String?): Boolean {
     return value != null && value.isNotBlank()
 }
 
-@ExperimentalContracts
-fun String?.or(alternative: String): String = if (isNotNullAndNotBlank(this)) this else alternative
+infix fun String?.or(alternative: String): String = if (isNotNullAndNotBlank(this)) this else alternative
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrSize.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrSize.kt
index 192960f..cfcb7d7 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrSize.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/model/validation/NullOrSize.kt
@@ -3,7 +3,6 @@ package dev.fyloz.trial.colorrecipesexplorer.model.validation
 import javax.validation.Constraint
 import javax.validation.ConstraintValidator
 import javax.validation.ConstraintValidatorContext
-import javax.validation.Payload
 import kotlin.reflect.KClass
 
 private const val MIN_SIZE = Long.MIN_VALUE
@@ -17,8 +16,7 @@ annotation class NullOrSize(
         val min: Long = MIN_SIZE,
         val max: Long = MAX_SIZE,
         val message: String = MESSAGE,
-        val groups: Array<KClass<*>> = [],
-        val payload: Array<KClass<out Payload>> = []
+        val groups: Array<KClass<*>> = []
 )
 
 class NullOrSizeValidator : ConstraintValidator<NullOrSize, Any> {
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/InventoryController.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/InventoryController.kt
index b6638ec..eae95da 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/InventoryController.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/InventoryController.kt
@@ -1,5 +1,5 @@
-//package dev.fyloz.trial.colorrecipesexplorer.rest
-//
+package dev.fyloz.trial.colorrecipesexplorer.rest
+
 //import dev.fyloz.trial.colorrecipesexplorer.model.InventoryMaterial
 //import dev.fyloz.trial.colorrecipesexplorer.service.InventoryService
 //import org.springframework.http.ResponseEntity
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/RestApiController.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/RestApiController.kt
index a45fa05..9c4392e 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/RestApiController.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/rest/RestApiController.kt
@@ -34,7 +34,7 @@ interface RestModelApiController<E : Model, S : EntityDto<E>, U : EntityDto<E>>
 
 abstract class AbstractRestApiController<E, N : EntityDto<E>, U : EntityDto<E>, S : ExternalService<E, N, U, *>>(
     val service: S,
-    protected val controllerPath: String
+    private val controllerPath: String
 ) :
     RestApiController<E, N, U> {
     protected abstract fun getEntityId(entity: E): Any?
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/AccountService.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/AccountService.kt
index 8200393..8240d29 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/AccountService.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/AccountService.kt
@@ -1,12 +1,12 @@
 package dev.fyloz.trial.colorrecipesexplorer.service
 
-import dev.fyloz.trial.colorrecipesexplorer.config.SecurityConfigurationProperties
 import dev.fyloz.trial.colorrecipesexplorer.config.blacklistedJwtTokens
 import dev.fyloz.trial.colorrecipesexplorer.config.defaultGroupCookieName
 import dev.fyloz.trial.colorrecipesexplorer.exception.model.EntityAlreadyExistsRestException
 import dev.fyloz.trial.colorrecipesexplorer.exception.model.EntityNotFoundException
 import dev.fyloz.trial.colorrecipesexplorer.exception.model.EntityNotFoundRestException
 import dev.fyloz.trial.colorrecipesexplorer.model.*
+import dev.fyloz.trial.colorrecipesexplorer.model.validation.or
 import dev.fyloz.trial.colorrecipesexplorer.repository.EmployeeGroupRepository
 import dev.fyloz.trial.colorrecipesexplorer.repository.EmployeeRepository
 import org.springframework.beans.factory.annotation.Autowired
@@ -170,13 +170,13 @@ class EmployeeServiceImpl(employeeRepository: EmployeeRepository, val passwordEn
         return update(with(entity) {
             Employee(
                 id = id,
-                firstName = if (firstName.isNotBlank()) firstName else persistedEmployee.firstName,
-                lastName = if (lastName.isNotBlank()) lastName else persistedEmployee.lastName,
+                firstName = firstName or persistedEmployee.firstName,
+                lastName = lastName or persistedEmployee.lastName,
                 password = persistedEmployee.password,
                 isDefaultGroupUser = false,
                 isSystemUser = false,
                 group = persistedEmployee.group,
-                permissions = if (permissions.isNotEmpty()) permissions.toMutableSet() else persistedEmployee.permissions,
+                permissions = permissions?.toMutableSet() ?: persistedEmployee.permissions,
                 lastLoginTime = persistedEmployee.lastLoginTime
             )
         })
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/InventoryService.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/InventoryService.kt
index 95b45d7..28c8888 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/InventoryService.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/InventoryService.kt
@@ -1,20 +1,12 @@
 package dev.fyloz.trial.colorrecipesexplorer.service
 
 import dev.fyloz.trial.colorrecipesexplorer.exception.TooLowQuantityException
-import dev.fyloz.trial.colorrecipesexplorer.model.InventoryMaterial
 import dev.fyloz.trial.colorrecipesexplorer.model.Material
 import dev.fyloz.trial.colorrecipesexplorer.model.dto.InventoryDto
-import dev.fyloz.trial.colorrecipesexplorer.model.toInventoryMaterial
 import org.springframework.stereotype.Service
 
-const val minimumQuantity = 100.0f  // TODO quantity stored in database
-
 @Service
 class InventoryService(val materialService: MaterialService) {
-    fun getAllMaterials(): Collection<InventoryMaterial> {
-        return materialService.getAllNotMixType().map { it.toInventoryMaterial(minimumQuantity) }
-    }
-
     /**
      * Use all materials in the given [mixes].
      * @throws TooLowQuantityException When there is not enough stock for a material
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/MaterialTypeService.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/MaterialTypeService.kt
index b4d36b2..81a4bc2 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/MaterialTypeService.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/MaterialTypeService.kt
@@ -105,8 +105,7 @@ class MaterialTypeServiceImpl(repository: MaterialTypeRepository, private val ma
 }
 
 @ResponseStatus(HttpStatus.CONFLICT)
-class CannotDeleteUsedMaterialTypeRestException : RestException(HttpStatus.CONFLICT) {
-    override val exceptionMessage: String = "Cannot delete a used material type"
-
+class CannotDeleteUsedMaterialTypeRestException :
+    RestException("Cannot delete a used material type", HttpStatus.CONFLICT) {
     override fun buildBody(): RestExceptionBody = object : RestExceptionBody() {}
 }
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/RecipeService.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/RecipeService.kt
index 27ce618..210d7f4 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/RecipeService.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/RecipeService.kt
@@ -19,7 +19,7 @@ interface RecipeService : ExternalModelService<Recipe, RecipeSaveDto, RecipeUpda
     /** Gets all recipes with the given [company]. */
     fun getAllByCompany(company: Company): Collection<Recipe>
 
-    /** Updates the public data of a recipe with the given [publicDateDto]. */
+    /** Updates the public data of a recipe with the given [publicDataDto]. */
     fun updatePublicData(publicDataDto: RecipePublicDataDto)
 
     /** Adds the given [mix] to the given [recipe]. */
diff --git a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/Service.kt b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/Service.kt
index c916344..1c6fc82 100644
--- a/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/Service.kt
+++ b/src/main/kotlin/dev/fyloz/trial/colorrecipesexplorer/service/Service.kt
@@ -11,7 +11,6 @@ import dev.fyloz.trial.colorrecipesexplorer.rest.RestApiController
 import io.jsonwebtoken.lang.Assert
 import org.springframework.data.jpa.repository.JpaRepository
 import org.springframework.data.repository.findByIdOrNull
-import kotlin.contracts.ExperimentalContracts
 
 /**
  * A service implementing the basics CRUD operations for the given entities.
@@ -144,6 +143,7 @@ interface ExternalNamedModelService<E : NamedModel, S : EntityDto<E>, U : Entity
     NamedModelService<E, R>, ExternalModelService<E, S, U, R>
 
 /** An [AbstractService] with the functionalities of a [ExternalService]. */
+@Suppress("unused")
 abstract class AbstractExternalService<E, S : EntityDto<E>, U : EntityDto<E>, R : JpaRepository<E, *>>(repository: R) :
     AbstractService<E, R>(repository), ExternalService<E, S, U, R>
 
diff --git a/src/test/kotlin/dev/fyloz/trial/colorrecipesexplorer/repository/RecipeStepRepositoryTest.kt b/src/test/kotlin/dev/fyloz/trial/colorrecipesexplorer/repository/RecipeStepRepositoryTest.kt
index 3bdd741..7d05f58 100644
--- a/src/test/kotlin/dev/fyloz/trial/colorrecipesexplorer/repository/RecipeStepRepositoryTest.kt
+++ b/src/test/kotlin/dev/fyloz/trial/colorrecipesexplorer/repository/RecipeStepRepositoryTest.kt
@@ -5,6 +5,7 @@ import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest
 import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager
 
+@Suppress("UNUSED_PARAMETER")
 @Disabled
 @DataJpaTest
 class RecipeStepRepositoryTest @Autowired constructor(