Add receipt/invoice email support and option to Quay

util/email.py

@@ -39,3 +39,11 @@ def send_recovery_email(email, token):
                 recipients=[email])
   msg.html = RECOVERY_MESSAGE % (token, token)
   mail.send(msg)
+
+
+def send_invoice_email(email, contents):
+  msg = Message('Quay.io payment received - Thank you!',
+                sender='support@quay.io',  # Why do I need this?
+                recipients=[email])
+  msg.html = contents
+  mail.send(msg)