* feat: notify_event_to_subscribers_task
* fix: avoid circular import, handle error
* fix: don't queue task in test mode
* fix: don't even send mail in test mode
* test: separately test signal
* fix: if/else error
* test: better naming
* test: test the new task
* test: better test name
* test: refactor notify email test
* fix: save, not update
* test: restore template coverage
