Value attribution codes were converted into UUIDs and stored
in the users, projects, api_keys, bucket_metainfos, and
value_attributions tables in the partner_id column. This
migration will lookup the appropriate partner name associated
with each of these UUIDs, and store the partner name directly
in the user_agent column within each table. If no corresponding
partner name exists for a partner_id, the partner_id value will
be stored instead.
Add migration for users table with tests.
Change-Id: I61254d9b81c474e76bcfc1c8cd863697c6ef44b6
