Explicitly save "never" frequency on NotificationPolicy. Closes #9720
Explicitly save "never" frequency on NotificationPolicy. Closes #9720

Previously, the rewritten Notification's page was deleting any
entries set to "never". However, some entries and code revert to the default behavior if no setting is recorded. This just makes each "never" setting be explicitly stored if set by the user.

Testing Plan:
============
* As a student set all notifications to "Do not send me anything"
* As a teacher create a new conference
* As a teacher go to Calendar -> Scheduler -> and create an appointment group
* Check the notification messages for the student
* Ensure that the student does not receive a notification message. (/users/x/messages)

Change-Id: Idbe4ad0d8b0394217787b5684161ab5987123e60
Reviewed-on: https://gerrit.instructure.com/12706
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Jon Jensen <44f878afe53efc66b76772bd845eb65944ed8232@instructure.com>

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