Event visibility schedule

[m-decarli]

Under events/*/edit/specification add the possibility to set a visibility start date and a visibility end date. Both should look like the registration start.

This should be separated for participants and organisers.

The start date is, when the event will be first visible to participants/organisers. The end date is when the event will be hidden for participants/organisers again.

These options should be locked after the event is set to "public".

Only admins can change the options in "public" state. Admins can also see an additional toggle, where they can manually override the visibility of the event.

[heddendorp]

Please explain what is tried to achieve here

[m-decarli]

For example, during the Orientation weeks, we want all events to be visible at the same time on a certain predefined date.

Currently, this is done manually by the Event manager, by setting all of them to 'public' at the same time, which can be a longer process, if there are 30+ events.

With this solution, the event can be set to 'public' once it is approved internally, but the event is still hidden for participants. After the set date, it will be automatically be visible to participants.