Handle cancelled preorders with a separate email

When a pre-order is cancelled from the Shopify admin it should also update in the Stoq pre-order menu/list too.

This should also be accompanied by a ‘Cancelled Order’ email, either from the existing Shopify email templates or giving the user an option to create an template email similar to ‘pre-order’ and ‘back-in-stock’.

Also to have the ability to manually send/trigger the ‘Pre-Order’ email notification per customer / bulk send to customers.