Auto calculate / create Prorated Refund Due for Subscriptions Cancelled Mid Term
When a subscription is cancelled during the middle of the term, the option to refund the prorated amount due back to the customer should exist. This feature exists partially when you change a subscription. When that happens, a credit note is created for the balance already paid and applied to a new invoice with the new amount. This is similar to cancellations - we shouldn't have to manually calculate the amount to be refunded.