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

As a nextcloud mail and calendar user,
I want that incoming mails which include an invitation are automatically added to a default calendar (per Mail Account).
Such that I don't miss any incoming invite anymore.

Describe the solution you'd like

There's two kind of mails I get with invites. One with .ics attachment, one with just the invite, mime type text/calendar.
Both should be processed by mail and added to a calendar that is specifically set as default calendar for each mail account.
MS Outlook processes events too. The behavior there is that it adds the invites to the calendar but does not trigger RSVP and leaves the item in the inbox, yet, it adds it to the calendar. Good default.

Describe alternatives you've considered

Add every new invite to a dedicated calendar just for mail (unprocessed)

Additional context

No response