Promo Codes for Active Builder Subscriptions#2734

Discount for Builder plans during an active subscription
Right now, discounts for Builder plans can only be applied to new subscriptions. However, it would be important to allow discounts for existing subscriptions as well. For example, users could apply a promo code while their subscription is active, and the discount would apply to the next billing cycle. So if someone uses a $10 promo code, their next payment would be reduced by $10.

A common issue with subscription-based systems is that they often focus only on new customers, while existing loyal users are not rewarded. It would be worth creating a simple system that also supports current subscribers.

The current workaround is inconvenient. Users have to cancel their subscription, wait for it to expire, and then subscribe again to use a promo code. This is not only frustrating for the user, but also risky for the business, since the user might not return after canceling.

Additionally, if the subscription expires and the user does not renew it immediately, their system may become unavailable, which could even lead to financial loss.

The solution is simple: existing subscribers should also be able to use promo codes. When a promo code is applied, the discount should automatically be deducted from the next billing cycle.