Return Merchandise Authorization Management - Link with MRP Kits

This module extends the RMA (Return Merchandise Authorization) functionality to work with kit products (phantom BoMs). When a customer requests a return from the sales order portal, they see the kit as a single line and can return the whole kit. Behind the scenes, Odoo creates individual RMAs for each component of the kit, linked together by a shared register.

• In the portal, kit lines are shown with a hidden kit product reference, and component lines are hidden from the customer. The customer only sees the kit and its quantity.
• In the backend, the RMA form and list views show the related kit product. The RMA report and portal page display kit information and list all related component RMAs.
• When refunding, the system checks that all component RMAs are received before allowing a refund. It then refunds the kit quantity, not the individual components, and marks all component RMAs as refunded.
• It prevents converting a cancelled kit RMA back to draft to avoid quantity inconsistencies.
• The sale order RMA wizard splits kit lines into component lines, and when creating RMAs, it validates that all components are available and calculates the correct quantities per kit.
• The module touches rma, sale.order, sale.order.line, account.move, and the RMA wizard models, adding fields like phantom_bom_product, kit_qty, and rma_kit_register.