feat(horses-service): remove legacy configuration and repository classes

- Deleted outdated `ApplicationConfiguration` and `HorseRepositoryImpl` classes.
- Migrated to streamlined modular Gradle configuration in `build.gradle.kts`.
- Updated domain models and dependencies to use multiplatform and serialization plugins.
- Added modular setup for `horses` namespace in `settings.gradle.kts`.
- Reorganized database configuration with minimal JDBC bindings for development.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

backend/services/horses/horses-domain/build.gradle.kts

@@ -1,9 +1,26 @@
 plugins {
-    kotlin("jvm")
+  alias(libs.plugins.kotlinMultiplatform)
+  alias(libs.plugins.kotlinSerialization)
 }
 
-dependencies {
-    implementation(projects.core.coreDomain)
-    implementation(projects.core.coreUtils)
-    testImplementation(projects.platform.platformTesting)
+kotlin {
+  jvm()
+
+  sourceSets {
+    commonMain {
+      kotlin.srcDir("src/main/kotlin")
+      dependencies {
+        implementation(projects.core.coreDomain)
+        implementation(projects.core.coreUtils)
+        implementation(libs.kotlinx.datetime)
+        implementation(libs.kotlinx.serialization.json)
+      }
+    }
+    commonTest {
+      kotlin.srcDir("src/test/kotlin")
+      dependencies {
+        implementation(projects.platform.platformTesting)
+      }
+    }
+  }
 }

backend/services/horses/horses-domain/src/main/kotlin/at/mocode/horses/domain/model/DomPferd.kt

@@ -1,16 +1,16 @@
 @file:OptIn(kotlin.uuid.ExperimentalUuidApi::class)
 package at.mocode.horses.domain.model
 
-import at.mocode.core.domain.model.PferdeGeschlechtE
 import at.mocode.core.domain.model.DatenQuelleE
+import at.mocode.core.domain.model.PferdeGeschlechtE
 import at.mocode.core.domain.serialization.KotlinInstantSerializer
 import at.mocode.core.domain.serialization.UuidSerializer
-import kotlin.uuid.Uuid
-import kotlinx.datetime.Clock
-import kotlinx.datetime.Instant
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.todayIn
 import kotlinx.serialization.Serializable
+import kotlin.time.Clock
+import kotlin.time.Instant
+import kotlin.uuid.Uuid
 
 /**
  * Domain model representing a horse in the registry system.
@@ -129,7 +129,7 @@ data class DomPferd(
      */
     fun getAge(): Int? {
         return geburtsdatum?.let { birthDate ->
-            val today = kotlinx.datetime.Clock.System.todayIn(kotlinx.datetime.TimeZone.currentSystemDefault())
+          val today = kotlin.time.Clock.System.todayIn(kotlinx.datetime.TimeZone.currentSystemDefault())
             var age = today.year - birthDate.year
 
             // Check if birthday has occurred this year
@@ -167,6 +167,6 @@ data class DomPferd(
      * Creates a copy of this horse with updated timestamp.
      */
     fun withUpdatedTimestamp(): DomPferd {
-        return this.copy(updatedAt = Clock.System.now())
+      return this.copy(updatedAt = kotlin.time.Clock.System.now())
     }
 }