Hold invites

[devmount]

Description of the Change

This change implements the previously discussed hold event flow.

This still needs heavy testing for both: Google and CalDAV.

Applicable Issues

Fixes #459

[devmount]

@MelissaAutumn This is still wip, but feel free to already take a look at it. Except for the remote event deletion, everythings already working fine on Google and CalDAV on my end.

[MelissaAutumn]

Fixed the issue. It turns out Google needs their internal id field to delete events, and not the one we create via their import method. So once we save an event it returns the event object back to us, so I just store it on appointment.external_id (new field!). CalDAV doesn't need to use this field, so it falls back to uuid.

Also discovered that it may fail if the user deletes their event before they reject the request. I'm not sure if we want to handle that any differently thank a "link is invalid" error. Additionally I discovered if you switch the schedule's calendar, delete and update requests were being attempted on the schedule's calendar and not the appointment's calendar (the one it's actually on.) so I patched that up.

Feel free to give it a try again to see if it all works on your end now!

[devmount]

Excellent work @MelissaAutumn 👏🏻 Google event deletion on denial works flawlessly now on my end too!

Also discovered that it may fail if the user deletes their event before they reject the request. I'm not sure if we want to handle that any differently thank a "link is invalid" error.

I think it's fine to keep that error for now and see, if we want to maybe make that more specific in the future if we need it.

Additionally I discovered if you switch the schedule's calendar, delete and update requests were being attempted on the schedule's calendar and not the appointment's calendar (the one it's actually on.) so I patched that up.

Oh, thank you! Didn't think of that particular case. Maybe we should also inform the user about open bookings when switching calendars on the schedule page or disabling them in the settings? Just as idea to improve the UX at that point, but out of scope here.

Imo we can merge this now.