Coupon Multiplier Free Product

This module extends the coupon and promotion features in Odoo with a new reward type named "Multiple of". It is meant for offers such as 3x2 or "take this product and get another one free" that apply repeatedly according to the promotion rules.

On the promotion form (the same screen where you configure promo programs), when you pick the "Multiple of" reward type you get extra options: - A "Force rewarded product" flag, which makes the free product mandatory in the sales order lines before the discount can be applied. - A "Max quantity" field, together with its unit of measure, to limit how many free reward products can be given (0 means no limit).

Automatic behaviours added by the code: - If you switch the reward type away from "Multiple of", the "Force rewarded product" flag is automatically turned off. - When you choose a reward product for a "Multiple of" promotion, the discount line product is set to that same product. - When the "Force rewarded product" flag is on, only the configured reward product is considered a valid product for the promotion. - When a coupon code is checked on a sales order, if the promotion is a "Multiple of" type with the forced product flag on and the reward product is not in the order lines, an error message is shown telling the user the reward products must be in the sales order lines to apply the discount.

The reward description shown for these promotions is displayed as "Free Product - <product name>". The module touches the coupon, promotion and reward models (coupon.coupon, coupon.program, coupon.reward) and the promotion form view.