Add MessageStream interface

Author: pennam

src/interfaces/MessageStream.h

@@ -0,0 +1,40 @@
+/*
+  This file is part of the ArduinoIoTCloud library.
+
+  Copyright (c) 2024 Arduino SA
+
+  This Source Code Form is subject to the terms of the Mozilla Public
+  License, v. 2.0. If a copy of the MPL was not distributed with this
+  file, You can obtain one at http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+/******************************************************************************
+ * INCLUDE
+ ******************************************************************************/
+
+#include <message/Commands.h>
+#include <functional>
+
+using upstreamFunction = std::function<void(Message*)>;
+
+/******************************************************************************
+ * CLASS DECLARATION
+ ******************************************************************************/
+
+class MessageStream {
+public:
+  MessageStream(upstreamFunction upstream): upstream(upstream) {}
+
+  /**
+   * Send message upstream
+   * @param m: message to send
+   */
+  virtual inline void sendUpstream(Message* m) {
+    upstream(m);
+  }
+
+private:
+  upstreamFunction upstream;
+};