Discounts are not enabled for subscriptions by default.

A discount should be also available for subscriptions in addition to the discount that is already set in the subscription.

E.G. a subscription has a 10% discount set. A regular discount is defined via promotion and is used for a reqular cart. When the same produdct is used in a subscription the discount from the promotion is not applied.

If a merchant want´s to apply both discounts within a subscription an option is needed in the promotion to use it also within subscritions.