update k3s flags

modules/nixos/my_k3s/default.nix

@@ -27,6 +27,10 @@ in
       type = types.nonEmptyStr;
       default = "server";
     };
+    extraFlags = mkOption {
+      type = types.listOf types.str;
+      default = [];
+    };
   };
 
   config = mkIf cfg.enable {
@@ -36,6 +40,7 @@ in
       tokenFile = cfg.tokenFile;
       clusterInit = cfg.clusterInit;
       serverAddr = cfg.serverAddr;
+      extraFlags = cfg.extraFlags;
     };
     environment.systemPackages = [ pkgs.nfs-utils ];
     services.openiscsi = {