* When a page is deleted, moderate associated
notifications. When it is undeleted, unmoderate.
* When a notification cannot be rendered
(canRender() returns false), moderate it.
The biggest advantage of moderation over mark-read-and-ignore
is that those notifications are filtered out at the database
level from this point on. They are not re-processed every single
time and do not affect the number of notifications returned by
the API.
Bug: T140327
Bug: T140836
Bug: T141463
Change-Id: Idefe78408fd584c13aaa9174cee3055539d92848
