nixos/plikd: Add new service module

nixos/modules/module-list.nix

···
   ./services/misc/paperless.nix
   ./services/misc/parsoid.nix
   ./services/misc/plex.nix
+  ./services/misc/plikd.nix
   ./services/misc/tautulli.nix
   ./services/misc/pinnwand.nix
   ./services/misc/pykms.nix

nixos/modules/services/misc/plikd.nix

···
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.plikd;
+
+  format = pkgs.formats.toml {};
+  plikdCfg = format.generate "plikd.cfg" cfg.settings;
+in
+{
+  options = {
+    services.plikd = {
+      enable = mkEnableOption "the plikd server";
+
+      openFirewall = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Open ports in the firewall for the plikd.";
+      };
+
+      settings = mkOption {
+        type = format.type;
+        default = {};
+        description = ''
+          Configuration for plikd, see <link xlink:href="https://github.com/root-gg/plik/blob/master/server/plikd.cfg"/>
+          for supported values.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.plikd.settings = mapAttrs (name: mkDefault) {
+      ListenPort = 8080;
+      ListenAddress = "localhost";
+      DataBackend = "file";
+      DataBackendConfig = {
+         Directory = "/var/lib/plikd";
+      };
+      MetadataBackendConfig = {
+        Driver = "sqlite3";
+        ConnectionString = "/var/lib/plikd/plik.db";
+      };
+    };
+
+    systemd.services.plikd = {
+      description = "Plikd file sharing server";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${pkgs.plikd}/bin/plikd --config ${plikdCfg}";
+        Restart = "on-failure";
+        StateDirectory = "plikd";
+        LogsDirectory = "plikd";
+        DynamicUser = true;
+
+        # Basic hardening
+        NoNewPrivileges = "yes";
+        PrivateTmp = "yes";
+        PrivateDevices = "yes";
+        DevicePolicy = "closed";
+        ProtectSystem = "strict";
+        ProtectHome = "read-only";
+        ProtectControlGroups = "yes";
+        ProtectKernelModules = "yes";
+        ProtectKernelTunables = "yes";
+        RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6 AF_NETLINK";
+        RestrictNamespaces = "yes";
+        RestrictRealtime = "yes";
+        RestrictSUIDSGID = "yes";
+        MemoryDenyWriteExecute = "yes";
+        LockPersonality = "yes";
+      };
+    };
+
+    networking.firewall = mkIf cfg.openFirewall {
+      allowedTCPPorts = [ cfg.settings.ListenPort ];
+    };
+  };
+}