Product Customer code for account invoice

When you create a customer invoice or credit note, each invoice line can display the product reference that this specific customer uses for that product, instead of only the internal product name. This is useful when a customer orders using their own article numbers and you want to see them on the invoice.

The module adds a computed "customer code" column on the invoice lines table, right after the product column. It only appears on sales documents (customer invoices and credit notes), not on vendor bills. The code is filled in automatically from the customer-specific product information stored on the product, based on the customer selected on the invoice. If no customer code is defined for that product and customer, the field stays empty.

No new menus or screens are added; the change appears directly inside the standard invoice form. The module touches account.move.line and the invoice form view. It relies on the customer product information feature provided by the product_supplierinfo_for_customer module, so that data must be configured on the product beforehand.