Audit - add ability to add a package as an auditor
Summary: Fixes T4687. This was also pretty easy...!
Test Plan: made a package with a test user as owner. added package as owner. looked right on commit page. logged in as test user and verified audit showed up on home page.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: chad, epriestley, Korvin
Maniphest Tasks: T4687
Differential Revision: https://secure.phabricator.com/D8705