message: Document login API
diff: @@ -78,6 +78,13 @@ export default class RtsClient {
  );
  }
  + /**
  + * Signal to the RTS that a login has occurred and that a user requires their team's
  + * token.
  + * @param {string} userId the user ID of the user who is a member of a team.
  + * @returns {Promise} a promise that resolves to { team_token: 'sometoken' } upon
  + * success.
  + */
  login(userId) {
  return request(this._url + '/login',
  {
  