Add secured subrouter for REST API

Rename IP filter option
Add array helper in util

internal/util/array.go

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 NHR@FAU, University Erlangen-Nuremberg.
+// All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+package util
+
+func Contains[T comparable](items []T, item T) bool {
+	for _, v := range items {
+		if v == item {
+			return true
+		}
+	}
+	return false
+}