The solution for HHH-10111 was to treat all converted (AttributeConverter) types as mutable so that dirty checking, deep copying and second-level caching all work properly no matter what.

However, treating these as immutable (when they really are) is more efficient. So allow the user some way to indicate whether a converted type is mutable or immutable.

Some initial ideas were:

• new optional contract to be implemented by the AttributeConverter impl.
• new annotation to be applied to the AttributeConverter impl