Please cherry-pick:

Please cherry-pick:
- if you don't want to have redundant entries (=objects aka. entities) in database of referenced entities, first you need to merge it as it is detached
- then you have a managed instance which you can set in the referencing entity back
- if you don't do this, the entity manager will "think" it is a new instance and persists + relinks it
- maybe some implementations don't do this, but the JPA standard (generic) seems to want to have this way
- do never implement for only one JPA implementation! Do always follow the generic JPA way