Fix some issues with Maniphest inbound email
Summary:
Fixes T3181.
- Inbound bugs@ mail is broken right now if it doesn't use the new external user stuff, because it calls $user->getPhabricatorUser() on an object which is already a PhabricatorUser. Instead, build the right $user object from the external user earlier on.
- Maniphest mail is nuking or otherwise awkwardly altering CCs. Make this work properly.
- Make sure "!unsubscribe" works correctly.
Test Plan: Sent bugs@ mail. Sent CC mail. Sent "!unsubscribe" mail.
Reviewers: btrahan, chad
Reviewed By: chad
CC: aran, tido
Maniphest Tasks: T3181
Differential Revision: https://secure.phabricator.com/D5911