To complete step-up authentication customer must be redirected to the issuing bank. This process is encapsulated within the redirect to stepUpUrl
returned in the PA enrollment response.
To initiate the redirect merchant must post step-up JWT to the stepUpUrl
displayed in an iframe:
Once customer completes the authentication Cardinal will redirect customer to ReturnUrl
set in the step-up JWT, this is similar to redirect to Term URL in 3DS1. When this redirect message is received merchant can close the iframe and proceed to PA Validation.