API: Fix to allow $0 transactions to properly process with a `payment_method_uri` passed in to the `cart`.
v2.0: PayPal Checkout (aka PayPal Commerce Platform) can now capture previously authorized transactions from the admin.
v2.0: PayPal Checkout (aka PayPal Commerce Platform) can now be used for subscription past-due reattempt processing.
INTERNAL: PayPal BN code is now properly passed.
v2.0: Improvements to Stripe’s card verification functionality.
v2.0: MercadoPago improvements for Columbian peso support.
v2.0: Improvement to handle currency conversion in certain shipping rate responses.
v2.0: Improvement to Skrill to better handle transactions after a payment error.
v2.0: Braintree anti-fraud functionality is now better supported, and the Braintree Kount integration can be enabled as well.