Defer submission feedback notifications for unavailable assignments

Prerequisites: A course with at least one enrolled student and one assignment activity. Assignment setting 'submissionreceipts' enabled for site. Test: Login as a student and submit to the assignment. The student should receive a submission notification (just to verify that notifications are being sent/received successfully). Login as a teacher and edit the assignment settings. In the 'Restrict access' section set 'Allow access from' to a time/date in the future. Give the student a grade and some feedback, making sure that 'Notify students' is set to 'No' and is frozen. Verify that the student does not receive feedback notification (allow enough time for the next assignment cron, according to your cron schedule). Edit the assignment settings again. In the 'Restrict access' section set 'Allow access until' to a time/date in the past. Verify again that the student does not receive feedback notification. Edit the assignment settings again, removing all access restrictions but hiding the assignment completely (using the visibility setting in 'Common module settings'). Verify again that the student does not receive feedback notification. Make the assignment visible. Verify that the student now receives the feedback notification.