Summary:
Ref T5791. This diff does a few things...
- Adds code to write recipients to edges on save
- Makes Query performance for policy filtering okay-ish
- Adds a Search Engine for PhabricatorMetaMTAMail
- Adds "working" List Controller
- Inbox and Outbox both work
- Adds stub View Controller
Test Plan: ran `./bin/storage upgrade` and saw my inbox and outbox start getting data. played with application and saw new entries in inbox and outbox
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Maniphest Tasks: T5791
Differential Revision: https://secure.phabricator.com/D13397
