The `.save()` method currently returns the given object as is. But with
Hibernate, it returns the corresponding object from the persistence
store, if any, which _may_ be different. This is causing some very hard
to debug and subtle bugs.
This fix here, to just ignore the result of `.save()` is not a permanent
fix, it's just a workaround that works well in both worlds, MongoDB and
Hibernate. Once we move though, we may need to revisit.
