TYPO3 Core

At the moment it is not possible to grant or deny read/write permissions on certain directories in the fileadmin folder.
When a user has access to a certain folder though a filemount, he can overwrite all files in the directory and subdirectories.

In order to be able to grant or deny write permissions to a certain user group on per directory basis it would be nice if one could configure read/write/overwrite permissions in the filemount settings (perhaps similar to the global file upload permissions available in the user access lists).

Usecase: ========
User Group A should be able to upload/update files in a certain folder.
User Group B must not be able to upload/overwrite files in that folder, but should be able to use the files uploaded by Group A.

This would be possible by creating 2 filemounts on the same folder. One with read/write permissions for Group A, and one with readonly permissions for Group B.

(issue imported from #M10743)