No Signer for Google Business App domain key & secret

The implementation for example from 
https://developers.google.com/accounts/docs/OAuth?hl=en#GoogleAppsOAuth is not 
working as there is no Signer for Google Apps domains key & secret.

#!/usr/bin/env php
<?php

require_once '../../src/Google_Client.php';

$key = 'domain.com';
$secret = '90kmsfglqiookfpok4apoAf';

$url = 
'http://docs.google.com/feeds/documents/private/full?xoauth_requestor_id=j.dow@d
omain.com';
$body = '<atom:entry xmlns:atom="http://www.w3.org/2005/Atom"><atom:category 
scheme="http://schemas.google.com/g/2005#kind" 
term="http://schemas.google.com/docs/2007#document" /><atom:title>Company 
Perks</atom:title></atom:entry>';
$method = 'POST';
$headers = ['Content-Type' => 'application/atom+xml'];
$request = new Google_HttpRequest($url, $method, $headers, $body);
$curl = new Google_CurlIO();

$response = $curl->authenticatedRequest($request);  // <- sign not yet 
implemented. No Signer for key, secret.
                            // Google_OAuth2->sign(Google_HttpRequest) works completely different.
                            // :((((((((((((((((((((
?>

Original issue reported on code.google.com by Evgeny.K...@gmail.com on 19 Apr 2013 at 9:06

User1010 / google-api-php-client

No Signer for Google Business App domain key & secret #308