code: function(user, passwd){
                  //setter only
  
                  validators.string(user);
                  validators.string(passwd);
                  data.auth = {
                      user : user,
                      passwd : passwd
                  };
  
                  return this;
              }
docs: <strong>Setter only</strong> to add authentication credentials to the request.
  
  @throws TypeError
  @param {String} user - the user name
  @param {String} passwd - the password value
  @returns {Aja} chains