cmd/tailscale/web: add support for QNAP

Signed-off-by: Maisem Ali <maisem@tailscale.com>

util/groupmember/groupmember.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package groupmemeber verifies group membership of the provided user on the
+// local system.
+package groupmember
+
+import (
+	"errors"
+	"runtime"
+)
+
+var ErrNotImplemented = errors.New("not implemented for GOOS=" + runtime.GOOS)
+
+// IsMemberOfGroup verifies if the provided user is member of the provided
+// system group.
+// If verfication fails, an error is returned.
+func IsMemberOfGroup(group, userName string) (bool, error) {
+	return isMemberOfGroup(group, userName)
+}