what happens when orders have both credit cards and billing accounts?

[Si Chen]

Hi.

We just noticed that if an order had a billing account  
(OrderHeader.billingAccountId) and a credit card associated with it,  
only the credit card should be charged.  This should be the right  
behavior if the billing account is used for wholesale customers as a  
line of credit, but if the billing account is a retail consumer's  
store credit (arising from a return), then most retailers would want  
the store credit used up first.

So, how about we add a ProductStore field to control whether the  
billing account should be used before other payment methods?

Si