PayPal support

[rgoj]

A while back we had a request for PayPal as a payment method. Tom looked into it with Chargebee and it wasn't trivial, IIRC. I'm raising this issue now as we've had another request for this - just to keep track of whether this is a growing need or not.

Here's the intercom thread where this was requested:
https://app.intercom.com/a/inbox/q3x5lnhp/inbox/conversation/106323200017755