Add 'en' locale for non-production warning

All the old LC_MESSAGES content from the old
preprodwarning module will have to be added...

locales/en/LC_MESSAGES/messages.po

@@ -1742,3 +1742,9 @@ msgstr ""
 "provide a SAML Authentication Response. Please note that this endpoint is"
 " not intended to be accessed directly."
 
+msgid "pre-production-warning"
+msgstr ""
+"You are now accessing a pre-production system. This authentication setup "
+"is for testing and pre-production verification only. If someone sent you "
+"a link that pointed you here, and you are not a tester you "
+"probably got the wrong link, and should not be here."