Implement payment through Swish

[isodude]

Swish is a Swedish payment provider where you pay through the mobile phone. (Vips in Norway).

What's needed is to implement either a simple QR code which you can scan, and/or the Swish Merchant API (https://github.com/olssonm/swish-php).

Regarding the QR Code implementation maybe that's another payment provider class, which is much simpler and that has a manual payment confirmation button admin-side (when someone pays I have to look at the actual mobile phone to see that the payment has gone through).

The Swish Merchant API actually handles the whole flow, much like credit card.