buildValidatePayload example

        $appPaymentMethod = $context->getPaymentMethod()->getAppPaymentMethod();
        if ($appPaymentMethod === null) {
            throw PaymentException::validatePreparedPaymentInterrupted('Loaded data invalid');
        }

        $validateUrl = $appPaymentMethod->getValidateUrl();
        if (empty($validateUrl)) {
            return new ArrayStruct();
        }

        $payload = $this->buildValidatePayload($cart, $requestDataBag, $context);
        $app = $appPaymentMethod->getApp();
        if ($app === null) {
            throw PaymentException::validatePreparedPaymentInterrupted('App not defined');
        }

        try {
            $response = $this->payloadService->request($validateUrl, $payload, $app, ValidateResponse::class, $context->getContext());
        } catch (ClientExceptionInterface $exception) {
            throw PaymentException::validatePreparedPaymentInterrupted(sprintf('App error: %s', $exception->getMessage()));
        }