[Feature] Allow Hiding of Calendar Events

[CommanderStorm]

Is your feature request related to a problem? Please describe.
When having multiple lectures in parallel, users would like to hide certain events ("I don't go there, therefore it would be helpful to not see it")

Describe the solution you'd like
The ability to hide and unhide events in the calendar

Describe alternatives you've considered
Marking them in a different colour

Additional context
Reported off platform via a private chat