code: function(serverName, config, options) {
      this.methods[serverName] = {};
      this.config.servers[serverName] = config;
      var self = this;
      ['valid_grant', 'treat_access_token', 'transform_token_response'].forEach(function(fctName) {
        self.methods[serverName][fctName] = options[fctName] || self[fctName].bind(self);
      });
    }
docs: Add oauth2 server