Update attendance status as organizer from web interface

Is your feature request related to a problem? Please describe.

Some users don't use emails clients that properly support invitations or give feedback in an unstructured way or using other channels like telephone, instant messenger etc. Those replies can't currently be tracked with Nextcloud Calendar and a separate list is needed.

Describe the solution you'd like

To avoid needing a separate attendance list it would be helpful if the organizer and members with edit permission could update the attendance status manually with the web interface. If this would be possible users could rely on the calendar attendance list and wouldn't have to keep two lists and those using groupware functions would get a better impression who will attend to a meeting and who won't. Currently the calendar is no reliable reference on who's attending and who's not.

Describe alternatives you've considered

Keeping a separate lists which is more complete than the list in the calendar.

Additional context

No response

No files, tests, or entry points are named in the issue. Clarify the web-interface scope and permission rules with maintainers before identifying an implementation path; done should allow organizers and members with edit permission to update attendance manually.