OZG-6259 warn when unmapped target field

vorgang-manager-server/src/main/java/de/ozgcloud/vorgang/collaboration/CollaborationRequestMapper.java

@@ -24,10 +24,11 @@
 package de.ozgcloud.vorgang.collaboration;
 
 import org.mapstruct.Mapper;
+import org.mapstruct.ReportingPolicy;
 
 import de.ozgcloud.vorgang.vorgang.GrpcCollaborationRequest;
 
-@Mapper
+@Mapper(unmappedTargetPolicy = ReportingPolicy.WARN)
 public interface CollaborationRequestMapper {
 
 	CollaborationRequest mapFrom(GrpcCollaborationRequest grpcCollaborationRequest);