Feature description

• Make it so that activities can be scheduled but not visible to anyone who is not an administrator but is a student (i.e. teachers, counselors, etc. can see them) before a specific date.

Rationale for adding feature

• Requested

Suggested implementation(s) (if applicable)

• Add a field when scheduling 8th period activities. It should be a datetime field, and use the existing calendar widget other datetime fields on Ion user. When trying to view an activity on a certain block from a student account before that datetime, they just shouldn't be able to see it. However, administrators and teachers etc. can still see it because it is scheduled.
• Activities should have a "hidden" tag assigned to them if they are currently hidden