With 2.2, I've begun implementing some write features in my app. I've started with voting. When you vote on a question on a site that isn't in a users associated accounts, you get the error "The account associated with the access_token does not have a user on the site." That makes sense, but is there a way to add a user to a site with the API? I notice that the official Android app pops up a dialog offering the user a chance to join the site in the same situation. Is that done via a private API?
If this isn't possible, consider this a feature request.