SAF: handle read-only-flag for files

[Thamos0815]

⚠️ Before posting ⚠️

• This is a bug, not a question or an enhancement.
• I've searched for similar issues and didn't find a duplicate.
• I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
• I agree to follow Nextcloud's Code of Conduct.

Steps to reproduce

1. Prepare a read-only file: Another user shares a file with the permissions restricted to read-only
2. In a 3rd-Party app: open the file from nextcloud using the system picker. I used KeepassDX
3. In 3rd-Party app: save a modified file.

Expected behaviour

1. The 3rd-Party app notices that it is opening the file as read-only and may propagate this to the user.
2. At latest, when trying to save the file, some error message should pop up.

Actual behaviour

1. The 3rd-Party app does not notice the permission-restriction. The file is opened for edit.
2. The 3rd-Party app can save a modified file.
3. Nextcloud App trys to synchronize the file. This results in transmission error "Berechtigungsfehler" (permission error?). The transmission is retried again and again, resulting in a sync-loop.
4. When the file is loaded again in the 3rd-Party app, the modified version is loaded.
5. The only way to recover i found was to delete the file in "Auf dem Gerät" (On the device?) locally. This way i lost the made changes. It took me quiet some time to discover, that i have to delete it there.

Android version

11

Device brand and model

Nokia 6.2

Stock or custom OS?

Stock

Nextcloud android app version

3.32.3

Nextcloud server version

30.0.12

Using a reverse proxy?

No

Android logs

No response

Server error logs

Additional information

i have no logging facilities set up. If you really need a log of this, i can try to set this up later.