In the explanation,
I think AssociationOverride is used when the value is an entity. I don't think we will use associationoverride to override the key.When the key or value is an entity, AssociationOverride is used.
Here is what the spec says:
The AttributeOverride(s) and AssociationOverride(s) annotations are
used to override the mappings for a map value that is an embeddable class.