Order with payment "stuck" in processing state when complete request fails

[LucaGallinari]

Steps to reproduce

• Mock the CompleteOrderApi::complete method to pass an additional header parameter to the capture action request so that Paypal will generate an error (doc: https://developer.paypal.com/docs/business/test-and-go-live/simulation-tests/#orders) like this:

        return $this->client->post(sprintf('v2/checkout/orders/%s/capture', $orderId), $token, null, [
            'PayPal-Mock-Response' => '{"mock_application_codes": "INSTRUMENT_DECLINED"}'
        ]);

• Place an order
• In "Pay with Paypal page" use the yellow paypal button, and confirm the payment on Paypal
• You will be redirected to the homepage, but if you try to retry the payment it will fail cause it's in "PROCESSING" state but the CreatePayPalOrderAction class try to load the last payment with "NEW" state and it won't find any.

Possible solution
This does not happen with HostedFields cause there is an additional check here that cancel the payment if it is still processing after the complete call.
But i think that this solution is weak. If, for example, the user closes the page while the capture request is going on, it will never call the cancel payment. Or maybe due to another error, the cancel payment url could never be called, and the payment of the order will remain PROCESSING.
Probably, it should be responsibility of the CompletePayPalOrderAction controller to cancel the payment if it failed. What do you think?

[LucaGallinari]

Generally, i think that the PayPalClient class should "handle" properly the cases in which Paypal return a response with a status code that is not 20X. Actually the Client only logs the error when that happen. Maybe it could throw exception and the classes that use the PayPalClient will catch that exception and operate consequently.

[jcgdjob]

When the payment status is "processing", and the paypal status is "captured", the cancel last payment should re-capture the payment instead of mark the payment as "canceled" as the actual payment has already been done.