$computedHash = base64_encode(hash_hmac ( 'md5' , $this->authServiceUrl , $this->password, true ));
$authorization = 'Authorization: Bearer '.$this->username.':'.$computedHash;
$curl = curl_init();
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, '');
curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type: application/json' , $authorization ));
curl_setopt($curl, CURLOPT_URL, $this->authServiceUrl);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);