Don't treat group folders like external folders. When group folders etc are added, prompt users to sync them

Currently, when a group folder/external folder/folder above 0.5 GB is added, the user just sees a notification, telling them that they have to subscribe to this folder.
At least three quarters of my users are non-techy, so they are not going to do this, unless I give them a hand. They have become accustomed to ignoring notifications until they go away. As a consequence, many of them miss out on whatever group folders are added.
I suggest that instead of a notification, there should be a prompt, were you can click "yes/not" and maybe "remind me later" as a third option.

See also https://github.com/nextcloud/groupfolders/issues/509