- This ensures content notifications are not translated to receiver
language.
- This adds actual plaintext support for content notifications (Was
previously just HTML as text view).
- Shares same base class across all mail notifications.
- Also cleaned up existing notification classes.
Future cleanup requested via #4501
Added test and changed logic to properly check the view permissions for
the notification receiver before sending.
Required change to permissions applicator to allow the user to be
manually determined, and a service provider update to provide the class
as a singleton without a specific user, so it checks the current logged
in user on demand.
- Updated mail notification design to be a bit prettier, and extracted
text to new lang file for translation.
- Added debounce logic for page update notifications.
- Fixed watch options not being filtered to current user.
