{ pkgs, lib ? pkgs.lib }:
let
  callPackage = lib.callPackageWith (pkgs // self);
  callPackageWithMerged = attrName: f: extraArgs:
    let
      mergedSubset = pkgs.${attrName} // self.${attrName};
      subsetArgs = builtins.listToAttrs [{ name = attrName; value = mergedSubset; }];
    in
    callPackage f (subsetArgs // extraArgs);
    self = rec {
      acme-dns = callPackage ./servers/acme-dns.nix {};
    };
in
self