add mailer relevant files, add pdf relevant files and confgurations for invoice generation and sending

app/jobs/notify_group_order_invoice_job.rb

@@ -0,0 +1,10 @@
+class NotifyGroupOrderInvoiceJob < ApplicationJob
+  def perform(group_order_invoice)
+    ordergroup = group_order_invoice.group_order.ordergroup
+    ordergroup.users.each do |user|
+      Mailer.deliver_now_with_user_locale user do
+        Mailer.group_order_invoice(group_order_invoice, user)
+      end
+    end
+  end
+end