location; this WILL BREAK configurations which are not updated accordingly.
In particular: any Transport use of $local_user which has been relying upon
check_local_user far away in the Router to make it safe, should be updated to
-replace $local_user with $local_part_verified.
+replace $local_user with $local_part_data.
Attempting to remove, in router or transport, a header name that ends with
an asterisk (which is a standards-legal name) will now result in all headers