Default billling address for "checkout as guest" GH2975
When a user buys books or merchandise and checks out as a guest, use the shipping address they entered as the billing address on the page where we collect their credit card information. Or maybe it's better if we add a "Billing address is same as shipping address" checkbox above the billing address fields. This seems like the better, more common user experience.
Do this for:
- Checking out without logging in, the multi-item "regular" shopping cart
- Placing a pre-order or backorder as a guest, the single-item shopping cart