docs: function get_client_registration(client_id) {
  
      return new Promise((resolve, reject) => {
          if (client_id === "123456") {
              return resolve({
                  redirect_uri_hostname: "localhost.sampleapp.com",
                  redirect_uri_port: "8443",
                  redirect_uri_path: "/sample_app/client_services",
                  description: "sample app",
                  client_id: client_id,
                  username: "test_client@clientcorp.com",
                  password: "client_pwd"
  
              });
          } else {
              return reject(new Error("client ID not registered!"));
          }
      });
  }