Improved Team handling in calendar invites

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

When I invite a team to a event there is no way to remove people again, even when they get removed from the team.

When I invite a team the calendar entry looks like this:

Even after I removed Elisabeth from the team and reload the calendar she is still shown as participant and there is no way to remove her. I could only remove the whole team. As a side note, also adding new people to the team doesn't add them to the calendar event

Describe the solution you'd like

I think it is not really possible to update calendar events when a team changse. We would need to check all calendar events from every user on every team change and update them if the team was invited to the event.

Therefore I would suggest a way simpler solution: Don't invite the team as one entity to a event. Instead just use the team as a short cut to select multiple people when creating a event. But when the event gets created we resolve the team member list and add them individually to the event. Btw, the same could be done with system groups, at the moment I can not invite a system group to a event.

This would have multiple benefits:

1. I can still quickly create a event for a large group of people by just selecting the team
2. Afterwards I could remove and add individual people as they join or leave the team
3. It would also work with external caldav clients. At the moment they only show a "circle-url" as invited person. With the suggested changes the user would also see all participants with third party calendar clients and could manage the participants list from everywhere.

Describe alternatives you've considered

Always update the event when a team changes, but as mentioned above I don't think this is possible in a performant way and it would not solve the third party client issue.

Additional context

No response

No files, tests, or entry points are named. Start by reproducing team invitation behavior in the calendar and tracing event creation and participant handling; done should be defined for removed and added team members, individual participant management, system groups, and third-party CalDAV clients.