code: function createUser(user, callback) {
        /* jshint validthis:true */
        var cb = callback || angular.noop;
  
        return User.save(user,
          function (data) {
            return cb(user);
          },
          function (err) {
            return cb(err);
          }.bind(this)).$promise;
      }
docs: @ngdoc function
  @name createUser
  @methodOf auth.service:Auth
  @description
  Create a new user
  
  @param {Object} user user info to use
  @param {Function} [callback] A callback
  @return {Promise} The promise of the User service