tiny optimization

user-manager-server/src/main/java/de/itvsh/kop/user/UserResourceMapper.java

@@ -80,9 +80,13 @@ public abstract class UserResourceMapper {
 
 	String mapId(UserResource userRes) {
 		var userRepresentation = userRes.toRepresentation();
-		var attributes = userRepresentation.getAttributes();
-		var id = attributes != null ? attributes.get(properties.ldapIdKey()) : null;
-		return id != null ? id.get(0) : userRepresentation.getId();
+
+		return Optional.ofNullable(userRepresentation.getAttributes())
+				.map(attributes -> attributes.get(properties.ldapIdKey()))
+				.filter(Objects::nonNull)
+				.map(id -> id.get(0))
+				.orElseGet(() -> userRepresentation.getId());
+
 	}
 
 	String mapEmail(UserResource userRes) {