Sale Promotion Coupon Module
############################

The sale_promotion_coupon module adds coupon to the promotions.

A promotion with coupons will be applied only if a linked coupon has been added
on the sale.

Promotion Coupon
****************

It defines the behaviours of a sets of coupon numbers for a promotion:

- *Name*: The name of the coupon.
- *Promotion*: The promotion to which the coupon is attached.
- *Number of Use*: How much time a coupon number can be used.
- *Per Party*: How the usage is counted.
- *Numbers*: The list of numbers which must be unique.