fix(userstatus): set user status to 'In a meeting' if calendar is busy

[miaulalala]

• Fixes: Set user status to busy when own calendar contains busy event #31177

Summary

A calendar query looks at the calendar to see if there are any events. TRANSPARENT calendars are ignored.

We ignore events if they're

• an OOO calendar event as that status is already handled
• a TRANSPARENT event
• an event that started before the user has set a custom status

We also do not overwrite a "DND" or "INVISIBLE" status or the Talk "In a Call" message.

How to test

• For OOO: set an OOO period and see that the OOO status stays persistent and is not overwritten by the calendar automation
• For calendar events: set an event in your calendar. Wait until it begins and wait until after it ends, status should be set to "In a meeting" and reset after. I use 5 / 10 minute events to test.
• For transparent calendar events - the same, see that the staus DOES NOT change to "In a meeting"
• For all day events, the status should stay "In a meeting" at all times unless overwritten by a custom status and should not revert back
• Overwriting with a custom status: See "In a meeting" status, set a custom status, reload. See that custom status still exists until next event.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[miaulalala]

/backport to stable28

[miaulalala]

Documentation: nextcloud/documentation#11405

[skjnldsv]

Please get this in asap if needed for 28.0.1