CB Paid Subscriptions

The basket skip behavior (only 1 payment gateway, no terms and conditions, and no invoice address) is still being applied even though a coupon code is available. The basket skip in this case shouldn't happen. This also leads into #8028 where you can't cancel your basket because it was skipped.

https://www.joomlapolis.com/forum/277-cb-paid-subscriptions-support/242645-coupon-code-not-showing-on-upgrade?start=6