No email notification when files have been uploaded into groupfolder

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Steps to reproduce

1. Create a groupfolder. Under personal settings > Notifications activate email notification for "A file or folder has been changed".
2. Have another user upload a file.
3. Wait for email notification about this new file.

Expected behaviour

Receive an email regarding the new file.

Actual behaviour

There is no email notification

Server configuration

Nextcloud version: Nextcloud Hub 9 (30.0.8)

I have noticed issue https://github.com/nextcloud/activity/issues/1889. But the problen also occurs with newly created groupfolders. (By the way that issue deals with the normal shares and they work fine).

I have activated "activity_use_cached_mountpoints" (see https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/activity_configuration.html#activities-in-groupfolders-or-external-storages). So generally, I receive email notification regards groupfolders (if a file has changed).

In WebGUI under "Activity" there are all the entries ("changed file", "deleted file", "created file"). But email notification only for "changed file" or "deleted file").

Why it doesn't send email notification regards "created file" or "deleted file"?

No source files or tests are named. Start by tracing how the Activity app handles created-file entries and email notifications for groupfolders, using the reported reproduction and the cached-mountpoints configuration as context; done means a newly uploaded groupfolder file produces the expected email without breaking existing activity emails.