v2.0: NEW PAYMENT GATEWAY: Square (SquareUp) support added.
v2.0: Improvements to PayPal Express Checkout non-Reference Transaction subscription cancellations.
v2.0: Improvement to Klarna error messaging.
v2.0: Improvement to next_transaction_date handling for subscription cancellations when the start date is in the future.
v2.0: Improvement to Klarna “cards” handling.