POS: exchange and return receipts

You can now process an exchange directly in the Point of Sale.

• One confirmation: the original ticket is returned and the replacement sale is created in the same step (no need to close the return then start a new sale).
• Documents: an invoice (FA) generates a credit note (Avoir); a delivery receipt (BL) generates a return receipt (Bon de retour). The replacement is a new POS sale.
• Net cash: if the new sale is higher, collect the difference; if it is lower, refund the difference; if amounts match, the drawer stays closed.
• An open cash session is required, as for any POS sale or return.