permissions: make calendar notifications user-mutable
Description
users that install a secondary Calendar app checking the same caldav source as the builtin Calendar app will see duplicate notifications.
They cannot silence the default Calendar app.
Screenshots
fixes being unable to disable:
Technical details
the notification permission for calendar is SYSTEM_FIXED:
android.permission.POST_NOTIFICATIONS: granted=true, flags=[ SYSTEM_FIXED|GRANTED_BY_DEFAULT|USER_SENSITIVE_WHEN_GRANTED|USER_SENSITIVE_WHEN_DENIED]
this MR removes that flag
Tests
- install Etar upstream
- set event in 6 minute with 5min alert
- get 2 notifications
after fix and disabling default Calendar notifications
- get 1 notification
Issues
closes e/backlog#905


