ctucx.git: dns.nix

fixup: Improve writeCharacterString docs

Show the type correctly (it had a wrong why from an earlier versions)
and explain more clearly what the function actually does, in particular
that it qutoes the string, so one doesn’t need to do it manually.

diff --git a/dns/util/default.nix b/dns/util/default.nix
@@ -14,8 +14,10 @@ let
       groupCount = (stringLength s - 1) / n + 1;
     in genList (i: substring (i * n) n s) groupCount;
 
-  # : str -> [str], such that each output str is <= 255 bytes
-  # (RFC 1035, 3.3)
+  # : str -> str
+  # Prepares a Nix string to be written to a zone file as a character-string
+  # literal: breaks it into chunks of 255 (per RFC 1035, 3.3) and encloses
+  # each chunk in quotation marks.
   writeCharacterString = s:
     if stringLength s <= 255
     then ''"${s}"''