The Auto-Create Support Campaign button was just showing an infinite "is
loading" spinner so you couldn't even click on it.
This fix allows the button to work again and only show the loading
spinner when it is actually loading.
See: https://meta.discourse.org/t/discourse-subscriptions/140818/653?u=blake
Adds full support to create coupon/promo codes in the Admin > Plugins > Subscriptions section of the plugin. The Create Coupon button opens a form on the same page, and the active checkboxes toggle the active status of the coupon code.