code: function create(user, callback) {
        var cb = callback || angular.noop;
  
        return User.create(user,
          function (user) {
            return cb(user);
          },
          function (err) {
            return cb(err);
          }).$promise;
      }
docs: @ngdoc function
  @name create
  @methodOf auth.user.service:UserService
  @description
  Save a new user
  
  @param {Object} user The userData to save
  @param {Function} [callback] A callback
  @returns {Promise} A promise