Express Checkout - Wallet Coupons / Rewards Integration

[angelleye]

Version 113.0 of the API introduced the ability to tie PayPal Wallet coupons / rewards, into Express Checkout. Need to get this tied into the plugin.

https://developer.paypal.com/webapps/developer/docs/classic/express-checkout/ht_ec-coupons-loyalty-programs/

[angelleye]

The guide covers the whole Express Checkout flow, but really all we're doing here is checking for some additional data that could be included in the GetExpressCheckoutDetails response, and if it is included, we would add that data to our DoExpressCheckoutPayment request so that it's included on the final order.