A bit late: you're correct, but it does provide a standard API for looking up additional metadata, even if it's non-standard. That's using custom claims and/or

A bit late: you're correct, but it does provide a standard API for looking up additional metadata, even if it's non-standard. That's using custom claims and/or the user info endpoint (which can include custom claims). You can use custom scopes to limit what is available as well.