feat(horses-service): remove integration tests and obsolete configurations

- Deleted outdated integration test classes (`HorseServiceIntegrationTest`, `TransactionalContextTest`, and others) and test resources (`logback-test.xml`).
- Removed obsolete Gradle dependencies related to these tests and revised project module references.
- Simplified `DomPferd` domain model with minor refactorings for serialization and validation.

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

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

@@ -6,6 +6,7 @@ import at.mocode.core.domain.model.PferdeGeschlechtE
 import at.mocode.core.domain.serialization.KotlinInstantSerializer
 import at.mocode.core.domain.serialization.UuidSerializer
 import kotlinx.datetime.LocalDate
+import kotlinx.datetime.number
 import kotlinx.datetime.todayIn
 import kotlinx.serialization.Serializable
 import kotlin.time.Clock
@@ -22,7 +23,7 @@ import kotlin.uuid.Uuid
  * @property pferdId Unique internal identifier for this horse (UUID).
  * @property pferdeName Name of the horse.
  * @property geschlecht Gender of the horse (Hengst, Stute, Wallach).
- * @property geburtsdatum Birth date of the horse.
+ * @property geburtsdatum Birthdate of the horse.
  * @property rasse Breed of the horse.
  * @property farbe Color/coat of the horse.
  * @property besitzerId ID of the current owner (Person from member-management context).
@@ -132,9 +133,10 @@ data class DomPferd(
           val today = kotlin.time.Clock.System.todayIn(kotlinx.datetime.TimeZone.currentSystemDefault())
             var age = today.year - birthDate.year
 
-            // Check if birthday has occurred this year
-            if (today.monthNumber < birthDate.monthNumber ||
-                (today.monthNumber == birthDate.monthNumber && today.dayOfMonth < birthDate.dayOfMonth)) {
+          // Check if a birthday has occurred this year
+          if (today.month.number < birthDate.month.number ||
+            (today.month.number == birthDate.month.number && today.day < birthDate.day)
+          ) {
                 age--
             }
 
@@ -164,7 +166,7 @@ data class DomPferd(
     }
 
     /**
-     * Creates a copy of this horse with updated timestamp.
+     * Creates a copy of this horse with an updated timestamp.
      */
     fun withUpdatedTimestamp(): DomPferd {
       return this.copy(updatedAt = kotlin.time.Clock.System.now())