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.
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.