mqtt: fix ci issue with prototypes

code/espurna/mqtt.h

@@ -17,6 +17,9 @@ Updated secure client support by Niek van der Maas < mail at niekvandermaas dot
 using mqtt_callback_f = std::function<void(unsigned int type, const char * topic, char * payload)>;
 using mqtt_msg_t = std::pair<String, String>; // topic, payload
 
+// TODO: need this prototype for .ino
+class AsyncMqttClientMessageProperties;
+
 #if MQTT_SUPPORT
 
 #if MQTT_LIBRARY == MQTT_LIBRARY_ASYNCMQTTCLIENT

code/espurna/mqtt.ino

@@ -606,7 +606,7 @@ bool _mqttMaybeSkipRetained(char* topic) {
 
 #if MQTT_LIBRARY == MQTT_LIBRARY_ASYNCMQTTCLIENT
 
-// MQTT Client can sometimes send messages in bulk. Even when message size is less than MQTT_MAX_PACKET_SIZE, we *could*
+// MQTT broker can sometimes send messages in bulk. Even when message size is less than MQTT_MAX_PACKET_SIZE, we *could*
 // receive a message with `len != total`, this requiring buffering of the received data. Prepare a static memory to store the
 // data until `(len + index) == total`.
 // TODO: One pending issue is streaming arbitrary data (e.g. binary, for OTA). We always set '\0' and expect text data.
@@ -636,7 +636,9 @@ void _mqttOnMessageAsync(char* topic, char* payload, AsyncMqttClientMessagePrope
 #else
 
 // Sync client already implements buffering. We *do need* to set '\0' to display stuff, though, so creating another buffer :)
-// TODO: Consider just not displaying stuff, most of the time it is hidden to the user of the device.
+// TODO: Consider just not logging or logging optionally, most of the time it is hidden to the user of the device.
+//       Callback receivers would need to expect the raw data and don't rely on things like strlen() / strcpy() / ... etc.
+// TODO: callback() would need to pass `len`
 
 void _mqttOnMessage(char* topic, char* payload, unsigned int len) {