Submit cancelled appointments correctly

[roquegv]

From Marcus:

If you save after cancelling a vacation request, the cancelled entry has simply disappeared in the new ICS file.

But now such a disappeared entry is then still displayed in the target calendar, because no updated entry with the matching UID is imported in the calendar.

First approach:
If you save after canceling a vacation request, the canceled entry has simply disappeared in the new ICS file.

But now such a disappeared entry is then still displayed in the target calendar, because no updated entry with the matching UID is imported in the calendar.

First approach:
The cancelled calendar entry must not be filtered out when it was before that booked, but the name must be prefixed with, for example, CANCELLED.

More elegant alternative:
The ICS file must also be regenerated when a previously booked appointment is cancelled.
The cancelled entry with its UID should now have the name or name prefix CANCELLED

Feel free to decide for yourself which implementation seems easier.

TODO:

• The ICS file must also be regenerated when a previously booked appointment is cancelled.
• The cancelled entry with its UID should now have the name or name prefix CANCELLED