expansion and serial fixes and new api

by HaxSam & WillyJL

applications/services/expansion/expansion.h

@@ -50,6 +50,15 @@ void expansion_enable(Expansion* instance);
  */
 void expansion_disable(Expansion* instance);
 
+/**
+ * @brief Check if an expansion module is connected.
+ *
+ * @param[in,out] instance pointer to the Expansion instance.
+ *
+ * @returns true if the module is connected and initialized, false otherwise.
+ */
+bool expansion_is_connected(Expansion* instance);
+
 /**
  * @brief Enable support for expansion modules on designated serial port.
  *