Removes database tables and functionality related to our custom
coupon implementation because it has been superseded by the Stripe
coupon and promo code system. Requires implementations of the
payments Invoices interface to return coupon usages along with
invoices.
Change-Id: Iac52d2ff64afca8cc4dbb2d1f20e6ad4b39ddfde
Jira: https://storjlabs.atlassian.net/browse/USR-822
This the last step of dropping these 2 db tables. It also deletes all
code associate with them.
Change-Id: I8be840dc2a7be255cf6308c9434b729fe4d9391e
