Added config for success fail redirect path

[kevinmeijer97]

Added some config to change the redirect path in case of a failed checkout.

[royduin]

Feedback from #774;

Maybe we should move all checkout configs to it's own file? @indykoning? Currently it's mixed:

• core/config/rapidez/frontend.php

  Line 28 in a554a07

  'checkout_steps' => [

• core/config/rapidez/system.php

  Line 31 in a554a07

  'standalone_checkout' => [

And should we use named routes here?

And @indykoning his reaction:

That might make the config nicer, do we see any other configs being added for the checkout in the future?
If it's just the 2 this is fine, if it becomes more maybe we should do the separate config.

Merging for now, maybe something for #769 to change this config + maybe change this to named routes in the future?