+ keyIncludes = builtins.concatStringsSep "\n" (map (v: "include \"${config.secrets.fullPaths."bind/${v}.key"}\";") (builtins.attrNames config.myEnv.dns.keys));
+ cartProduct = lib.foldr
+ (s: servers: servers // { ${s.masters} = lib.unique ((servers.${s.masters} or []) ++ [s.keys]); })
+ {}
+ (lib.unique (lib.concatMap (z: cartesianProductOfSets { masters = z.masters or []; keys = z.keys or []; }) config.myEnv.dns.slaveZones));