This method allows to quickly convert a username of a known account to an ID that can be used with the REST API, or to check if a username is available for sign-up
Update the user's display and preferences.
Test to make sure that the user token works.
Creates a user and account records. Returns an account access token for the app that initiated the request. The app should save this token for later, and should wait for the user to confirm their account by clicking a link in their email inbox.