I succeeded with persisting the proposed format. But when reading back I don't know that the given value actually is for the column addresses_id, so I seem not to be able to re-construct the association row in the correct form (we don't have the information about all the column names in the association/row key metadata).

I think we could resolve the issue by adding information about all the column names to AssociationKeyMetadata. In this case we'd restore the value to the only column which is not part of the association nor the row key. Any thoughts?