Better way to handle continue URL in payment callback

[bjarnef]

Is your feature request related to a problem? Please describe.
Currently ProcessCallback method in PaymentProviderBase doesn't have easy access to e.g. continue URL like for example GenerateForm.

For now we can set a property in meta data for PaymentFormResult in GenerateForm and then access this property in ProcessCallback:

var continueUrl = order.Properties["myPaymentProviderContinueUrl"]?.Value;

Could we handle this in another way or have a utility method to access this?

Describe the solution you'd like
It would be great to have a utility method or similar to easier access continue URL, cancel URL and error URL in ProcessCallback method as some payment gateway only accept a return URL, which most likely will be the callback URL, where you need to handle the redirection yourself.

[mattbrailsford]

I've been thinking about this myself too as there are a few providers that need access to those URL's in non GenerateForm methods. Thanks for raising the issue, I'll use this to track progress when we get to it 👍