Add section at the bottom of invoice: Payment Description at Checkout

- If there is any payments, we use the last one to retrieve the payment method description
Use the first completed payment to display payment description
Completed is state = "checkout" or state = "completed"
Squash w/ "Add section at the bottom of invoice: Payment Description at Checkout"

Squash w "Add section at the bottom of invoice: Payment Description a"

app/views/spree/shared/_payment.html.haml

@@ -13,3 +13,8 @@
     = t :email_payment_summary
 - if @order.payments.any?
   = render partial: 'spree/shared/payments_list', locals: { payments: @order.payments }
+  - if last_payment_method(@order).present?
+    %p.callout{style: "margin-top: 40px"}
+      %strong
+        = t :email_payment_description
+    %p{style: "margin: 5px"}= last_payment_method(@order).description

config/locales/en.yml

@@ -1669,6 +1669,7 @@ See the %{link} to find out more about %{sitename}'s features and to start using
   email_order_summary_includes_tax: "(includes tax):"
   email_payment_paid: PAID
   email_payment_not_paid: NOT PAID
+  email_payment_description: Payment Description at Checkout
   email_payment_summary: Payment summary
   email_payment_method: "Paying via:"
   email_so_placement_intro_html: "You have a new order with <strong>%{distributor}</strong>"