Enhancement: Show available service types when setting up a provider
The Online Accounts panel does not show any indication as to which services are available from a provider until after authenticating. This leads to the user wondering, "What parts of my Google/Microsoft/Nextcloud account can I actually connect to GNOME?"
The information at https://wiki.gnome.org/Projects/GnomeOnlineAccounts/Providers should ideally be part of the panel UI. A summary like "Calendar, Contacts, Files" could appear on the connect button similar to the way the user's login name appears below the label on accounts that are already connected. Or if that's too cluttered, it could be shown as a caption in the pop-up to authenticate.
Showing this information before authenticating is useful because it can tell the user whether it's worth going to the trouble of connecting an account. If they know from the start that they can connect to a provider's mail but not files, and what they want is to connect to their files, they can just skip on by. Or if they do want to connect mail, they know from the start that it's possible.