R1:b7297a3278c6

Add an "Author's projects" Herald field to Differential

Summary:
Ref T1279. This allows installs to implement two different flavors of project review. They can either implement this rule:

When:
[ ... ] [ ... ]
Take Action:
[ Add blockign reviewers ] [ Security ]

...which means "every revision matching X needs to be signed off by someone else on the Security team, //even if the author is on that team//". The alternative is to implement this rule:

When:
[ Author's projects ] [ do not…