public function setOAuthCredentials(array $config) 
    {
        // @todo change by using ConfigVO
        // Throw exeception for mandatory params
        if (!isset($config['client_id'])) {
            throw new \InvalidArgumentException('Missing client_id.');
        }

        // Throw exeception for mandatory params
        if (!isset($config['client_secret'])) {
            throw new \InvalidArgumentException('Missing client_secret.');
        }

        // Throw exeception for mandatory params
        if (!isset($config['bearer'])) {
            throw new \InvalidArgumentException('Missing client_secret.');
        }
    }