Allow duplicates of items if they're in a contingency grou

[dcruize]

For example if someone is selling two items and I want both.

Item 1 will sell for around ÂGBP 20, with ÂGBP 5.50 p&p.
Item 2 will sell for around ÂGBP 4, with ÂGBP 5.50 p&p.

I'll put in a snipe for the first item at ÂGBP 21.x and ÂGBP 5.x for the second item. However, I'd like to also add the second item again but in a contingency group with the first item. If I win the first item, I'll not need to pay the p&p on the second item so the second snipe could be for ÂGBP 9 which should be a guaranteed win.

This is a feature I'd use all the time since the items I buy often come from sellers clearing out their collections, but the delicate nature of a lot of the items means p&p can be a lot for a low value item.

Thanks for making Gixen, you really helped me start a business during Covid that kept a roof over my head!