nixos: create 'modules/nixos' folder

Let's consolidate all modules under one path, so that NixOS,
home-manager, and nix-darwin (if I ever end up using it down the line)
would go under the same folder.

modules/nixos/services/jellyfin/default.nix

@@ -0,0 +1,39 @@
+# A FLOSS media server
+{ config, lib, ... }:
+let
+  cfg = config.my.services.jellyfin;
+in
+{
+  options.my.services.jellyfin = {
+    enable = lib.mkEnableOption "Jellyfin Media Server";
+  };
+
+  config = lib.mkIf cfg.enable {
+    services.jellyfin = {
+      enable = true;
+      group = "media";
+    };
+
+    # Set-up media group
+    users.groups.media = { };
+
+    my.services.nginx.virtualHosts = [
+      {
+        subdomain = "jellyfin";
+        port = 8096;
+        extraConfig = {
+          locations."/" = {
+            extraConfig = ''
+              proxy_buffering off;
+            '';
+          };
+          # Too bad for the repetition...
+          locations."/socket" = {
+            proxyPass = "http://127.0.0.1:8096/";
+            proxyWebsockets = true;
+          };
+        };
+      }
+    ];
+  };
+}