Setter method setMqttClientName

[markreds81]

Added a setter method to set mqttClientName property after instantiation. This allows to use a custom string built at runtime, for example, add the ESP mac address as suffix. See the following example:

char hostname[12];
EspMQTTClient client("MySSID", "MyPass", "5.196.95.208", NULL, NULL, NULL,  1883);

void setup() {	
	byte mac[6];
	WiFi.macAddress(mac);
	sprintf(hostname, "MyThing-%02X%02X", mac[4], mac[5]);
	client.setMqttClientName(hostname);
}

[plapointe6]

Thanks for your contribution.
This will work if you call setMqttClientName() in the setup() before any loop() calls.

Merged