Associated entities of self-referential entities with uuid ids fail to save

Apologies that this is quite complex. If you have:

• A tree-like self-referential relationship, e.g. X hasMany X
• A hasMany List relationship on X to some other entity type, e.g. X hasMany Y
• Y belongsTo X
• X uses a uuid generator for its id

Saving the top level X with a graph of objects underneath it will fail with

org.springframework.dao.InvalidDataAccessApiUsageException: object references an unsaved transient instance - save the transient instance before flushing: Y

If the X hasMany Y is a Set this does not happen. It does happen if X has a single Y when Y does not have a belongsTo declared.

This is a regression from 2.0.3 where this worked fine.

Please see the attached example project with failing test.