CompletePurchaseResponse

Hi Ambroise, 

In complete purchase response your getTransactionId should get the authorisationId field, there is no orderId key in the returned array

 ```
   /**
     * Get the transaction ID as generated by the merchant website.
     *
     * @return string
     */
    public function getTransactionId()
    {
        return $this->fields['authorisationId'];
    }
```