After a user has been authenticated at an OAuthProvider's web page, the provider will redirect the browser to the provided redirectUrl. The provider will add a query parameter to the redirectUrl called "code" that represent the authorization code for the user. This method will use the authorization code to validate the user and fetch the user's email address from the OAuthProvider. If there is no existing account using the email address from the provider then a new account will be created, the user will be authenticated, and an access token will be returned. If the email address from the provider is already associated with an account or if the passed user name is used by another account then the request will return HTTP Status 409 Conflict.