We have added a new option to the coupon settings: it is now possible to limit the application scope of a coupon to specific billable metrics.
By default, coupons apply to all charges but when creating a new coupon, you can define the list of billable metrics to which the coupon applies.
This feature is related to the
billable_metric_codes attribute of the
coupon object (see API documentation).
Please refer to the guide for more information on coupons.