Sale Product Pack Fixed Discount

This is a bridge module that makes the product pack feature and the fixed discount feature work together on sales orders.

When you sell a product pack, the pack is split into a main line and component lines. This module adds a hidden technical flag on each sales order line that tells Odoo whether the product is a pack, whether the line belongs to a pack, and whether the pack's components can be modified.

Based on those flags, the fixed discount field on the order line behaves differently:

• On the order line form, the fixed discount field is hidden when the line is a pack itself, or when the line is not linked to a pack at all. In other words, it only appears for component lines of a pack.
• In the order lines list, the fixed discount field is read-only for pack lines and for component lines of packs whose components cannot be modified. It stays editable only for component lines of packs that allow modifiable components.

All of this happens directly on the standard sales order screen (sale.order), in the order lines section. No new menus, reports, emails or scheduled actions are added. The module only changes the visibility and editability of the fixed discount field, so users cannot apply a fixed discount to a whole pack or to locked pack components.