Recurrent events in Google calendar (shared as “Free/Busy”) do not block slots in availability check

[woolfg]

Description

I am using “Check for conflicts in ...” on an external Google cal (shared as “Free/Busy” so I do not see any details).
For single events all works as expected but recurrent events to not block slots if there is a busy event at the same time in the external google cal.

Steps to Reproduce

1. Connect an external Google Calendar (shared as Free/Busy only)

2. Enable in settings:“Check for conflicts in ...” ans select the external cal.

3. In the Google Calendar, create a weekly recurring event that marks time as busy.
   When shared as Free/Busy only, Google provides data similar to this:

   BEGIN:VEVENT
   DTSTART:20251015T060000Z
   DTEND:20251015T070000Z
   DTSTAMP:20251103T132806Z
   UID:52b23a92-e505-4ef5-a6d2-1beb7125f5e1
   ATTENDEE;X-NUM-GUESTS=0:mailto:user@example.com
   RECURRENCE-ID:20251015T060000Z
   SUMMARY:Busy
   END:VEVENT
   BEGIN:VEVENT
   DTSTART:20251022T060000Z
   DTEND:20251022T070000Z
   DTSTAMP:20251103T132806Z
   UID:52b23a92-e505-4ef5-a6d2-1beb7125f5e1
   ATTENDEE;X-NUM-GUESTS=0:mailto:user@example.com
   RECURRENCE-ID:20251022T060000Z
   SUMMARY:Busy
   END:VEVENT
   BEGIN:VEVENT
   DTSTART:20251029T070000Z
   DTEND:20251029T080000Z
   DTSTAMP:20251103T132806Z
   UID:52b23a92-e505-4ef5-a6d2-1beb7125f5e1
   ATTENDEE;X-NUM-GUESTS=0:mailto:user@example.com
   RECURRENCE-ID:20251029T070000Z
   SUMMARY:Busy
   END:VEVENT
   BEGIN:VEVENT
   DTSTART:20251105T070000Z
   DTEND:20251105T080000Z
   DTSTAMP:20251103T132806Z
   UID:52b23a92-e505-4ef5-a6d2-1beb7125f5e1
   ATTENDEE;X-NUM-GUESTS=0:mailto:user@example.com
   RECURRENCE-ID:20251105T070000Z
   SUMMARY:Busy
   END:VEVENT
   BEGIN:VEVENT
   DTSTART:20251112T070000Z
   DTEND:20251112T080000Z
   DTSTAMP:20251103T132806Z
   UID:52b23a92-e505-4ef5-a6d2-1beb7125f5e1
   ATTENDEE;X-NUM-GUESTS=0:mailto:user@example.com
   RECURRENCE-ID:20251112T070000Z
   SUMMARY:Busy
   END:VEVENT

4. Open the Appointments page in Nextcloud and check availability for the corresponding dates and times.

Other Settings:

• Time slot mode : weekly template

Possible Cause?

Google’s Free/Busy export does not include a true recurring RRULE entry.
Instead, it publishes a series of individual VEVENTs with identical UIDs and varying RECURRENCE-IDs.

Environment

• Nextcloud version: Nextcloud Hub 10 (31.0.8)
• Appointments version: 2.6.1
• Calendar app version: 5.5.8

P.S. thanks for the great app and your work!

[SergeyMosin]

Most likely related to #398
The fix for it is somewhat complicated but it is a high priority issue for v3.