Contrary to other payment acquirers all transactions through stripe are
s2s transactions. Because of this payment_stripe has to create it's own
payment.transactions which is unusual.
Because of this payment_stripe needs a sale order id which will be
provided by website_sale in request.session. website_quote doesn't do
this so this extracts it from the return_url, just like
website_quotation.js does.
opw-678117
Christophe Matthieu