Add refund email to invoice export

Is your feature request related to a problem? Please describe. I use pure crowdfunding app without woocommerce integration. The problem is that in invoice view, I cannot see and especially export the refund email address field, which is the only contact information for customer that I have.

Describe the solution you’d like I’d like to have an option to easily export the list of paid invoices with the selected perk and e-mail address that they gave during payment.

Describe alternatives you’ve considered Running:

docker exec -it c59817c0f6fe psql -U postgres btcpayservermainnet

select "CustomerEmail" from "Invoices" where "OrderId" like 'crowdfund-app%' and "Status"='complete'  order by "Created";

[pavlenex]

I think we just need to add refund email to the invoice export.

[jooray]

Both are great. I think exporting refund email should be there as well, in case they differ, it is good to see that in the export.