Automated response: Stock control can get locked up

The shopping cart does not do a good job of clearing out orders that are never completed. This includes intermediate orders when managing the shopping cart.

This locks up stock control.

This is a bit complex to clean up as we have to also avoid over-sales, and the potential for clearing out orders that are currently being purchased if the user accidentally refreshes their cart in another tab.

We will have to assume that payment signals (IPNs) are truly instant or that customers won't come in and create a new cart while waiting for a prior order's IPN to come through. This assumption is better than locking up the stock unnecessarily.

FYI orders only stay locked in for a day, after that it assumes they aren't going to be purchased and stock is returned to availability. We'll make the timing configurable in v10.