refactor: moved nixos modules to dendrite pattern

modules/nixos/programs/jellyfin/jellyfin.nix

@@ -0,0 +1,34 @@
+{...}: {
+  flake.nixosModules.jellyfin-service = {
+    lib,
+    pkgs,
+    config,
+    ...
+  }: let
+    jellyfinPort = 8096;
+    dlanPort = 1900;
+  in {
+    options.services.jellyfin = {
+      media_directory = lib.mkOption {
+        type = lib.types.str;
+        description = "directory jellyfin media will be hosted at";
+        default = "/srv/jellyfin/media";
+      };
+    };
+
+    config = lib.mkIf config.services.jellyfin.enable {
+      environment.systemPackages = [
+        pkgs.jellyfin
+        pkgs.jellyfin-web
+        pkgs.jellyfin-ffmpeg
+      ];
+
+      networking.firewall.allowedTCPPorts = [jellyfinPort dlanPort];
+
+      systemd.tmpfiles.rules = [
+        "d ${config.services.jellyfin.media_directory} 2770 jellyfin jellyfin_media"
+        "A ${config.services.jellyfin.media_directory} -    -        -               - u:jellyfin:rwX,g:jellyfin_media:rwX,o::-"
+      ];
+    };
+  };
+}