Calendar notifications on participant change are misleading

Steps to reproduce

1. Be part of an event
2. Have another participant change their participation
3. Get a mail about it

Expected behavior

The email should communicate clearly what it is about. E.g. "Andy Scherzinger declined attendance", with the event details below.

(If the email is even needed.)

Actual behavior

Periodically I get a bunch of what seems like automated invitation mails about repeating events. They say that "Daphne" or "Stephan" or someone else updated the event, but since they are at the same time they seemed automated.

@ChristophWurst explained:

Andy triggered this. He rejected attendance. The change goes to the organizer, then propagates to the attendees.

Calendar app version

6.5.0

CalDAV-clients used

No response

Browser

No response

Client operating system

No response

Server operating system

Our cloud.nc

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

34.0.1

Updated from an older installed version or fresh install

None

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

Very similar issue: https://github.com/nextcloud/calendar/issues/8487

Start by reading the related issue #8487, then trace the calendar notification path for participant changes. Compare the current email with the reported reproduction; done means the message clearly identifies the participant's attendance change and includes the event details, or the project has decided that no email is needed.