Not possible to use Idempotency Key in checkout API / PaymentLinks

[floddy-newport]

Describe the bug
The idempotency key is not set in the request header, because Adyen\Service\AbstractResource::requestHttp does not pass the requestOptions param.

To Reproduce

1. Install library.
2. Use Adyen\Service\ResourceModel\Checkout\PaymentLinks::create with the $requestOptions set to ['idempotency' => ].
3. Uxing xdebug or similar, see how the $requestOptions param is lost along the way and not sent in the header.

Expected behavior
The request options should be passed to Adyen\HttpClient\CurlClient::requestHttp and the idempotency key should be sent in the header of the request.

[floddy-newport]

Upon further work with implementation I realised that this implementation is deprecated and to use Adyen\Service\Checkout\PaymentLinksApi::paymentLinks instead.