R1:f8080ce93142

Add CustomField support to Owners

Summary: Fixes T9351. This is straightforward since this application is now relatively modern and doesn't have any bizarre craziness.

Test Plan:
{F787981}

{F787982}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9351

Differential Revision: https://secure.phabricator.com/D14093