I'm developing a shop. I'm trying to figure out: where should "total_grand_price" belong to?
"total_grand_price" = price of all order items - discount + shipping + taxex +- etc....
Should it be a property of Order or Invoice? What up- and downsides of having it in either?
Also, could there be a case where there'll be several different invoices with a different TotalGrandPrice for the same Order? When can it happen?