Klarna Payments Authorization Callback

Problem/Motivation

Klarna provides a (new?) callback for the authorization code: https://docs.klarna.com/payments/web-payments/integrate-with-klarna-paym...
Klarna also sent out mails to clients to implement this in their payment gatways with the subject: "Action required - Integration update to support Authorization Callback"

Proposed resolution

As far as I understand, two things need to be done:

• implement the endpoint and somewhere store the authorization_token and session_id on the order
• also allow the submission of the redirect form if no authorization_token was obtained?

We would provide a patch, maybe someone can approve if we are going the right direction