Auto discovery deactivation at runtime by MQTT command (#856)

and switch automatic creation for it in HASS (by autodiscovery :-)

docs/upload/advanced-configuration.md

@@ -52,3 +52,30 @@ home/OpenMQTTGateway/SRFBtoMQTT/59365 {"raw":"2B660186042E00E7E5","value":"59365
 ```
 
 It can be usefull to avoid warning or errors on certain controllers.
+
+## Auto discovery
+Home Assistant discovery is enabled by default on all binaries and platformio configurations except for UNO. With Arduino IDE you have to uncomment [ZmqttDiscovery](https://github.com/1technophile/OpenMQTTGateway/blob/0180a0dbd55ed8e0799e30ee84f68070a6f478fa/User_config.h#L99) in User_config.h. 
+
+To have a working discovery setup you need to enable it on your MQTT integration definition in HASS.
+
+::: tip
+With platformio you can deactivate discovery by adding:
+``` ini
+'-UZmqttDiscovery="HADiscovery"'
+```
+To your environment definition.
+:::
+
+So as to create the MQTT username and password, you have to create a new user(recommended) into Home Assistant->Configuration->Users (available in admin mode) or use an existing username/pwd combination (not recommended). This user doesn't need to be an administrator.
+
+![](../img/OpenMQTTGateway-Configuration-Home-Assistant.png)
+
+::: warning
+The max size of the username is 30 and 60 for the password.
+:::
+
+OMG will use the auto discovery functionality of home assistant to create sensors and gateways into your HASS instance automaticaly.
+
+The gateway device will be available into Configuration->Devices section of Home Assistant.
+
+![](../img/OpenMQTTGateway_Home_Assistant_MQTT_discovery.png)