feat(nix-flake): add nix flake and nix module

nix/services.nix

@@ -0,0 +1,51 @@
+{config, lib, pkgs, ...}:
+
+with lib;
+
+let
+  cfg = config.services.discord-tweeter;
+
+  format = pkgs.formats.toml { };
+  configFile = format.generate "config.toml" cfg.settings;
+in
+{
+  options.services.discord-tweeter = {
+    enable = mkEnableOption (lib.mdDoc "discord-tweeter");
+
+    settings = mkOption {
+      type = format.type;
+      default = {
+        username = "";
+        password = "";
+        proxyaddr = "";
+        webhook = "";
+        DbPath = "/var/lib/discord-tweeter/";
+        CookiePath = "/var/lib/discord-tweeter/";
+        channels = [  ];
+        filter = [ 0b11111 ];
+        UseWebServer = true;
+        HostURL = "";
+        WebPort = 8080;
+        UserAgents = [ "discordbot" "curl" "httpie" "lwp-request" "wget" "python-requests" "openbsd ftp" "powershell" ];
+        NitterBase = "https://xcancel.com";
+      };
+      description = lib.mdDoc ''
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.discord-tweeter = {
+      description = "Send tweets to Discord by scraping Twitter (now X)";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        DynamicUser = true;
+        ExecStart = "${self.packages.${pkgs.system}.default}/bin/discord-tweeter ${configFile}";
+        Restart = "on-failure";
+      };
+    };
+  };
+}
+