CA: field is missing in .narinfo files #53
Description
Unlike cache.nixos.org, nix-serve's .narinfo files have no CA: field.
As the result, FOD's downloaded from nix-serve are not marked as FOD locally.
It is a minor issue which have subtle consequences you may hit years after: it breaks nothing until you perform an action which depends on whether a derivation FOD or not (e.g. you may want to prevent FODs from being GC'ed and suddenly you have no way to distinguish them reliably)