fix reference to PersistPostfachNachrichtByCommandServiceTest

vorgang-manager-server/src/test/java/de/ozgcloud/vorgang/command/PersistPostfachNachrichtByCommandServiceTest.java

@@ -188,7 +188,8 @@ class PersistPostfachNachrichtByCommandServiceTest {
 
 		@Test
 		void shouldThrowException() {
-			assertThatThrownBy(() -> service.findAnswers(serviceKontoType, PostfachAddressTestFactory.STRING_BASED_IDENTIFIER_POSTFACH_ID_VALUE,
+			assertThatThrownBy(
+					() -> service.findAnswers(serviceKontoType, PostfachAddressTestFactory.IDENTIFIER.toString(),
 							GrpcPostfachMailTestFactory.REFERENCED_NACHRICHT_ID))
 									.isInstanceOf(UnsupportedOperationException.class);
 		}