OZG-7473 add validation messages and change collection

Sub task: OZG-7933

src/main/java/de/ozgcloud/admin/AdministrationRepositoryRestConfigurer.java

@@ -34,9 +34,12 @@ import de.ozgcloud.admin.common.DelegatingValidatorAdapter;
 @Configuration
 public class AdministrationRepositoryRestConfigurer implements RepositoryRestConfigurer {
 
+	private static final DelegatingValidatorAdapter DELEGATING_VALIDATOR_ADAPTER = new DelegatingValidatorAdapter(
+			Validation.buildDefaultValidatorFactory().getValidator());
+
 	@Override
 	public void configureValidatingRepositoryEventListener(ValidatingRepositoryEventListener listener) {
-		var validator = Validation.buildDefaultValidatorFactory().getValidator();
-		listener.addValidator("beforeCreate", new DelegatingValidatorAdapter(validator));
+		listener.addValidator("beforeCreate", DELEGATING_VALIDATOR_ADAPTER);
+		listener.addValidator("beforeSave", DELEGATING_VALIDATOR_ADAPTER);
 	}
 }