Add email invites to Phabricator (logic only)


Add email invites to Phabricator (logic only)

Ref T7152. This builds the core of email invites and implements all the hard logic for them, covering it with a pile of tests.

There's no UI to create these yet, so users can't actually get invites (and administrators can't send them).

This stuff is a complicated mess because there are so many interactions between accounts, email addresses, email verification, email primary-ness, and user verification. However, I think I got it right and got test coverage everwhere.

The degree to which this is exception-driven is a little icky, but I think it's a reasonable way to get the testability we want while still making it hard for callers to get the flow wrong. In particular, I expect there to be at least two callers (one invite flow in the upstream, and one derived invite flow in Instances) so I believe there is merit in burying as much of this logic inside the Engine as is reasonably possible.

Test Plan: Unit tests only.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7152

Differential Revision: https://secure.phabricator.com/D11723