Allow specifying price record reference which is copied to order line

As a business use with complex price lists model I would like YC to be able to record the price list reference on order lines so that I can better understand the price determination mechanism once the order was placed.

The price reference could be a contract number or a special marker that should be visible in order view in JAM.

TD:

• add additional column priceRef on SkuPrice, which can be amended in JAM.
• adjust cart prices calculation mechanism so that SkuPrice.priceRef is saved on cart object and then later on added as custom value on the order lines under "ItemPriceRef" (similar to ItemCostPrice)