Better error message when bookmarks app not enabled on the server.
Currently, when trying to connect the app to a Nextcloud server where the Bookmarks app is (mistakenly) not enabled, a generic “Connection failed” message suggesting to check Internet access, wherethe the URL is correct and self-signed certificates is displayed.
A better error message would inform the user that the app is currently not enabled on the server. This can be detected by the fact the Nextcloud core returns a 302 status in this case.