public function tokenAction()
    {
        // Can't do anything if not HTTP request...
        if (!$this->request instanceof HttpRequest) {
            return null;
        }

        // Currently, ZF2 Http Request object is not PSR-7 compliant, therefore we need to create a new one from
        // globals, and then convert the response back to ZF2 format

        $request  = ServerRequestFactory::fromGlobals();
        $response = $this->authorizationServer->handleTokenRequest($request);

        return $this->convertToZfResponse($response);
    }