feat(UserMountCache): Emit events for added, removed and updated mounts

[provokateurin]

Summary

Closes #49881

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[come-nc]

Small question but otherwise looks promising

[kyteinsky]

hello,
Nice, these events should be exhaustive.

There are a few issues, however:

1. files:scan or load/reload of the files page emits the UserMountAddedEvent with mountpoint /<userid>/ for all the user ids scanned
   Here is a call stack for all the files:scan event:
   

2. Share creation to a user/group does not emit any mount events. The ShareCreatedEvent event is emitted however.
   All the users have at logged in at least once.
   The mount events are emitted when the user logs in or there is a files:scan for that particular user.
   It is the same case with share deletions.

files:scan after share creation:

{"reqId":"pmngY1441revF6CjXJnp","level":3,"time":"2025-02-05T09:58:32+00:00","remoteAddr":"","user":false,"app":"context_chat","method":"","url":"--","message":"UserMountAddedEvent","userAgent":"--","version":"32.0.0.0","data":{"app":"context_chat","mountPoint":"/eve/"}}
{"reqId":"pmngY1441revF6CjXJnp","level":3,"time":"2025-02-05T09:58:32+00:00","remoteAddr":"","user":false,"app":"context_chat","method":"","url":"--","message":"UserMountAddedEvent","userAgent":"--","version":"32.0.0.0","data":{"app":"context_chat","mountPoint":"/eve/files/Flusspferd.pdf/"}}

subsequent files:scan's

{"reqId":"cGhw83SLMlaMVRYoz5Ud","level":3,"time":"2025-02-05T09:59:12+00:00","remoteAddr":"","user":false,"app":"context_chat","method":"","url":"--","message":"UserMountAddedEvent","userAgent":"--","version":"32.0.0.0","data":{"app":"context_chat","mountPoint":"/eve/"}}

3. For groupfolders, user "admin" already had access to the groupfolder gf1. When group "alpha" is granted access to the same groupfolder, UserMountAddedEvent is emitted for only the user "admin":

{"reqId":"mrFnNx8E1hlmpUmsAxht","level":3,"time":"2025-02-05T10:00:38+00:00","remoteAddr":"192.168.21.6","user":"admin","app":"context_chat","method":"POST","url":"/index.php/apps/groupfolders/folders/1/groups","message":"UserMountAddedEvent","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36","version":"32.0.0.0","data":{"app":"context_chat","mountPoint":"/admin/"}}

Removal of group "alpha" has the same result, UserMountAddedEvent is emitted for user "admin".
No files:scan was done here at any time.

Allowing the group "delta" access to the groupfolder and doing a files:scan then emits the UserMountAddedEvent events for all the users of the group "delta", in addition to all users' root mounts, as said before.

4. Testing with Teams (circles), similar to groupfolders and normal shares, no event is emitted when a share is created.
   No normal share event is received either.
   Also similar to groupfolders, the Added and Removed events show up on files:scan.

5. Exactly similar observations with external storage

Let me know if you need more logs for any particular series of steps.

[provokateurin]

/backport to stable31

[provokateurin]

/backport to stable30