fix(nixos): run Valheim with storage group

configs/nixos/hosts/pikachu/default.nix

@@ -7,15 +7,6 @@
 # pikachu — AZW ME Pro server.
 # Disk layout is in ./disk.nix.
 # `fileSystems` for the root disk are derived from it.
-let
-  valheimSteamRun = pkgs.steam-run.override {
-    extraBwrapArgs = [
-      "--bind"
-      "/pikachu"
-      "/pikachu"
-    ];
-  };
-in
 {
   imports = [
     ./hardware-configuration.nix
@@ -83,8 +74,9 @@ in
       appId = 896660;
       installDir = "/pikachu/data/servers/valheim/main";
       workingDirectory = "/pikachu/data/servers/valheim/main";
+      group = "storage";
       dataDirs = [ "/pikachu/media/games/servers/valheim/main" ];
-      packages = [ valheimSteamRun ];
+      packages = [ pkgs.steam-run ];
       environment = {
         SteamAppId = "892970";
         SERVER_PASSWORD = "foobarbaz";

configs/nixos/modules/services/steamcmd.nix

@@ -245,9 +245,10 @@ in
         ]
         ++ lib.flatten (
           lib.mapAttrsToList (_: app: [
-            "d ${app.installDir} 0770 ${cfg.user} ${cfg.group} - -"
-            "z ${app.installDir} 0770 ${cfg.user} ${cfg.group} - -"
-          ]) enabledApps
+            "d ${app.installDir} 0770 ${app.user} ${app.group} - -"
+            "z ${app.installDir} 0770 ${app.user} ${app.group} - -"
+          ] ++ map (dataDir: "d ${dataDir} 0770 ${app.user} ${app.group} - -") app.dataDirs
+            ++ map (dataDir: "z ${dataDir} 0770 ${app.user} ${app.group} - -") app.dataDirs) enabledApps
         );
 
       systemd.services = lib.mkMerge (