Performance optimization of owned_tag_set / tag_set_nomination Edit

Changed the model to identify owned_tag_sets and tag_set_nominations to be identified by user_id rather then pseud_id.

Updated the methods involved, and made a migration task to preserve existing data and make the change.

Ran the pre-existing test for tag_set_nominations which uses the other models, and it passed.

net result, removes unneeded table joins, increasing performance