PayPal integration

[dsevolve23]

https://www.paypal.com/us/smarthelp/article/what-is-the-difference-between-payment-data-transfer-(pdt)-and-instant-payment-notification-(ipn)-faq2934

[DanWin]

@dsevolve23 A link without any comment or context doesn't exactly say much. I assume you want to have a PayPal integration as also mentioned in #66 correct?