[Bug]: Calendar reminder notification shows wrong calendar for the event

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I got a notification for a reminder I set on a event in calendar A, but the notification said it is in calendar B. I double checked and the event is definitely in calendar A and not B.

Steps to reproduce

Not tested, but this should work?

1. Create calendar A
2. Create calendar B
3. Create event in calendar A, set reminder
4. Wait for reminder notification

Expected behavior

The notification should show the correct calendar the event is from.

Installation method

Community Docker image

Nextcloud Server version

26

Operating system

Other

PHP engine version

PHP 8.1

Web server

Nginx

Database engine version

PostgreSQL

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

/

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start by reproducing the reported scenario: create calendars A and B, add a reminder to an event in A, and inspect the notification after it fires. Trace how the reminder notification determines the event's calendar, then verify that the notification names calendar A rather than calendar B.