code: function () {
      _options.auth0 = merge(
        _options.auth0,
        {
          domain: process.env.AUTH0_DOMAIN,
          clientID: process.env.AUTH0_CLIENT_ID,
          clientSecret: process.env.AUTH0_CLIENT_SECRET
        }
      );
    }
docs: begin private methods /*
  This is called by module constructor and is used to load Auth0 config
  variables from environment variables.