Product Code Mandatory

This module changes how product references work in Odoo. The Internal Reference field on products becomes mandatory, so users can no longer save a product without a code.

Where it appears: - On the standard product form, the Internal Reference field is now required. - On the product template form, the field is required only when the product has a single variant; when a product has several variants, the field is hidden there and the code is managed on each variant instead. - On the product variant form, the Internal Reference is always required.

Automatic behaviour: - When a new product is created, the Internal Reference is pre-filled with a number taken from a dedicated sequence, with the prefix DEFAULT- followed by four digits (for example DEFAULT-0001). Users can overwrite it with their own code. - The sequence is defined once at installation and is shared across companies.

Business effect: every product ends up with a unique internal reference, which helps with identification, searching and reporting. The module only touches the product models (product.product and the product template form) and does not add new menus or screens of its own.