technitium-dns-server: fix inaccessible state directory (#383225)

nixos/modules/services/networking/technitium-dns-server.nix

···
 
 let
   cfg = config.services.technitium-dns-server;
-  stateDir = "/var/lib/technitium-dns-server";
   inherit (lib)
     mkEnableOption
     mkPackageOption
···
       after = [ "network.target" ];
 
       serviceConfig = {
-        ExecStart = "${cfg.package}/bin/technitium-dns-server ${stateDir}";
+        ExecStart = "${cfg.package}/bin/technitium-dns-server $STATE_DIRECTORY";
 
         DynamicUser = true;
 
         StateDirectory = "technitium-dns-server";
-        WorkingDirectory = stateDir;
-        BindPaths = stateDir;
 
         Restart = "always";
         RestartSec = 10;

nixos/tests/technitium-dns-server.nix

···
     machine =
       { pkgs, ... }:
       {
+        systemd.services.technitium-dns-server.serviceConfig.Restart = lib.mkForce "no";
+
         services.technitium-dns-server = {
           enable = true;
           openFirewall = true;