add dufs (webdav) module

modules/dufs.nix

@@ -0,0 +1,52 @@
+{ config, pkgs, lib, ... }:
+
+let
+  cfg = config.services.dufs;
+in
+{
+  options.services.dufs = {
+    sharedPath = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      description = "Path to the folder to share via WebDAV. Set to null to disable dufs.";
+      example = "/mnt/storage/shared";
+    };
+
+    port = lib.mkOption {
+      type = lib.types.port;
+      default = 5099;
+      description = "Port to listen on";
+    };
+
+    auth = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      description = "Basic authentication in format 'username:password'. Will be automatically formatted for dufs.";
+      example = "admin:secret123";
+    };
+  };
+
+  config = lib.mkIf (cfg.sharedPath != null) {
+    # Install dufs package
+    environment.systemPackages = [ pkgs.dufs ];
+
+    # Create systemd service
+    systemd.services.dufs = {
+      description = "Dufs WebDAV File Server";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      serviceConfig = {
+        Type = "simple";
+        User = "root";  # Run as root to access any system path
+        ExecStart = "${pkgs.dufs}/bin/dufs ${cfg.sharedPath} --port ${toString cfg.port} --bind 0.0.0.0"
+          + lib.optionalString (cfg.auth != null) " --auth ${cfg.auth}@/:rw";
+        Restart = "on-failure";
+        RestartSec = "10s";
+      };
+    };
+
+    # Open firewall port (optional, since traffic comes through WireGuard)
+    # networking.firewall.allowedTCPPorts = [ cfg.port ];
+  };
+}