dnscrypt-proxy: Make FHS compliant and fix cache (#448491)

nixos/modules/services/networking/dnscrypt-proxy.nix

@@ -67,7 +67,7 @@ in
             ${
               if cfg.upstreamDefaults then
                 ''
-                  ${pkgs.buildPackages.remarshal}/bin/toml2json ${pkgs.dnscrypt-proxy.src}/dnscrypt-proxy/example-dnscrypt-proxy.toml > example.json
+                  ${pkgs.buildPackages.remarshal}/bin/toml2json ${pkgs.dnscrypt-proxy}/etc/dnscrypt-proxy/dnscrypt-proxy.toml > example.json
                   ${pkgs.buildPackages.jq}/bin/jq --slurp add example.json $jsonPath > config.json # merges the two
                 ''
               else

pkgs/by-name/dn/dnscrypt-proxy/package.nix

@@ -2,6 +2,7 @@
   lib,
   buildGoModule,
   fetchFromGitHub,
+  fetchpatch,
   nixosTests,
 }:
 
@@ -20,6 +21,18 @@ buildGoModule rec {
     hash = "sha256-JPBAlRpJw6Oy4f3twyhX95XqWFtUTEFPjwyVaNMSHmQ=";
   };
 
+  patches = [
+    (fetchpatch {
+      url = "https://gitlab.archlinux.org/archlinux/packaging/packages/dnscrypt-proxy/-/raw/main/0001-Make-configuration-file-hierarchy-compliant.patch";
+      hash = "sha256-qsbKcgeB/g388TERH8nYy/kfMSN5a21fbUoa80ZMgW4=";
+    })
+  ];
+
+  postInstall = ''
+    mkdir -p $out/etc/dnscrypt-proxy
+    cp dnscrypt-proxy/example-dnscrypt-proxy.toml $out/etc/dnscrypt-proxy/dnscrypt-proxy.toml
+  '';
+
   passthru.tests = { inherit (nixosTests) dnscrypt-proxy; };
 
   meta = with lib; {