Better $1 and $0 transactions support

#1

I believe Curve could process authorisation requests way better. Currently, the process is unclear and raises many questions like these: Zero value authorizations. The very nature of Curve and the way it works makes refunds more complicated (the merchant sends a refund to Curve and then Curve needs to refund it to the underlying card, which is an extra cost and hassle to everyone).

So, knowing that zero value auth and 1$/€/ £/etc. are usually going to be refunded anyway, Curve shouldn’t even charge them on the underlying card at all! We know it’s possible for hotel/car rental authorisations, which are usually way higher of value, so there should be no problem implementing the same solution for very small authorisation requests. Obviously, if such transaction finally goes through and the hold isn’t reversed by the merchant, it would need to go through on the originally chosen underlying card.