[Bug]: Activities generated for calendar shared with group but unshared individually

⚠️ 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 OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

In the daily activity summary email I get notifications about a shared calendar that I have unshared for myself with the "unshare for me" button in the calendar app.
The calendar is shared by another user to a group, that contains myself.

Probably this code should filter out the unshared calendars:
https://github.com/nextcloud/server/blob/master/apps/dav/lib/CalDAV/Activity/Backend.php#L616-L621
Similar to what is done here:
https://github.com/nextcloud/server/blob/b24a917d4370d09ff810bbcf42b60508b54fb7f4/apps/dav/lib/DAV/Sharing/SharingMapper.php#L28

Steps to reproduce

1. User A: Share a calendar with a group that contains user B
2. User B: enable calendar activity email notifications
3. User B: Do "unshare for me" on the shared calendar
4. User A: Create an event in the calendar
5. User B gets an email notification, despite having unshared the calendar.

Expected behavior

When unsharing a calendar, that is shared to a group, no activity emails should be received from that calendar.

Nextcloud Server version

30

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

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

Upgraded to a MAJOR version (ex. 28 to 29)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

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

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "cloud.mydomain.ch",
            "werkzeug.mydomain.ch"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "30.0.2.2",
        "overwrite.cli.url": "https:\/\/cloud.mydomain.ch",
        "overwriteprotocol": "https",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance": false,
        "theme": "",
        "loglevel": 1,
        "updater.release.channel": "stable",
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "ssl",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "social_login_auto_redirect": true,
        "htaccess.RewriteBase": "\/",
        "simpleSignUpLink.shown": false,
        "default_phone_region": "CH",
        "skeletondirectory": "",
        "templatedirectory": "",
        "defaultapp": "files,calendar",
        "app_install_overwrite": [
            "extract",
            "impersonate",
            "talk_matterbridge",
            "issuetemplate",
            "keeweb"
        ],
        "memcache.local": "\\OC\\Memcache\\APCu"
    }
}

List of activated Apps

Enabled:
  - activity: 3.0.0
  - announcementcenter: 7.0.1
  - app_api: 4.0.0
  - calendar: 5.0.5
  - circles: 30.0.0
  - cloud_federation_api: 1.13.0
  - comments: 1.20.1
  - contacts: 6.1.1
  - dashboard: 7.10.0
  - dav: 1.31.1
  - deck: 1.14.2
  - drawio: 3.0.3
  - external: 5.5.2
  - federatedfilesharing: 1.20.0
  - files: 2.2.0
  - files_downloadlimit: 3.0.0
  - files_fulltextsearch: 30.0.0
  - files_pdfviewer: 3.0.0
  - files_reminders: 1.3.0
  - files_sharing: 1.22.0
  - files_trashbin: 1.20.1
  - files_versions: 1.23.0
  - forms: 4.3.3
  - fulltextsearch: 30.0.0
  - group_everyone: 0.1.16
  - groupfolders: 18.0.5
  - impersonate: 1.17.0
  - integration_google: 3.1.0
  - keeweb: 0.6.20
  - logreader: 3.0.0
  - lookup_server_connector: 1.18.0
  - mail: 4.0.3
  - notifications: 3.0.0
  - oauth2: 1.18.1
  - photos: 3.0.2
  - polls: 7.2.5
  - privacy: 2.0.0
  - provisioning_api: 1.20.0
  - recommendations: 3.0.0
  - related_resources: 1.5.0
  - richdocuments: 8.5.2
  - settings: 1.13.0
  - sociallogin: 5.7.0
  - tables: 0.8.1
  - tasks: 0.16.1
  - text: 4.1.0
  - theming: 2.5.0
  - timemanager: 0.3.16
  - twofactor_backupcodes: 1.19.0
  - updatenotification: 1.20.0
  - user_status: 1.10.0
  - viewer: 3.0.0
  - webapppassword: 24.9.0
  - webhook_listeners: 1.1.0-dev
  - workflowengine: 2.12.0
Disabled:
  - admin_audit: 1.20.0 (installed 1.9.0)
  - appointments: 2.3.1 (installed 2.3.1)
  - assistant: 2.1.1 (installed 2.1.1)
  - backup: 1.4.0 (installed 1.4.0)
  - bruteforcesettings: 3.0.0 (installed 1.6.0)
  - collectives: 2.15.1 (installed 2.15.1)
  - contactsinteraction: 1.11.0 (installed 1.0.0)
  - documentserver_community: 0.1.20 (installed 0.1.20)
  - emlviewer: 1.0.11 (installed 1.0.11)
  - encryption: 2.18.0
  - extract: 1.3.6 (installed 1.3.6)
  - federation: 1.20.0 (installed 1.9.0)
  - files_external: 1.22.0 (installed 1.20.0)
  - files_mindmap: 0.0.30 (installed 0.0.30)
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - firstrunwizard: 3.0.0 (installed 2.8.0)
  - fulltextsearch_elasticsearch: 30.0.0 (installed 30.0.0)
  - integration_whiteboard: 0.0.14 (installed 0.0.14)
  - maps: 1.5.0 (installed 1.5.0)
  - nextcloud_announcements: 2.0.0 (installed 1.14.0)
  - onlyoffice: 9.5.0 (installed 9.5.0)
  - password_policy: 2.0.0 (installed 1.9.1)
  - passwords: 2024.11.20 (installed 2024.11.20)
  - serverinfo: 2.0.0 (installed 1.9.0)
  - sharebymail: 1.20.0 (installed 1.19.0)
  - snappymail: 2.38.2 (installed 2.38.2)
  - spreed: 20.0.2 (installed 20.0.2)
  - support: 2.0.0 (installed 1.2.1)
  - survey_client: 2.0.0 (installed 1.7.0)
  - suspicious_login: 8.0.0
  - systemtags: 1.20.0 (installed 1.9.0)
  - talk_matterbridge: 1.26.0 (installed 1.26.0)
  - twofactor_nextcloud_notification: 4.0.0
  - twofactor_totp: 12.0.0-dev
  - user_ldap: 1.21.0 (installed 1.7.0)
  - weather_status: 1.10.0 (installed 1.1.0)

Nextcloud Signing status

Nextcloud Logs

Additional info

Additional User Backend: Social Login

Start by reading apps/dav/lib/CalDAV/Activity/Backend.php around lines 616-621 and compare the filtering in apps/dav/lib/DAV/Sharing/SharingMapper.php around line 28. Reproduce the group-shared calendar and “unshare for me” steps, then verify that creating an event no longer generates an activity email for the unshared calendar.