Set online/offline as last will & testament #4
Description
Hopefully this is a minor change to mqtt.h connect call - see upstream docs at https://pubsubclient.knolleary.net/api#connect to add in some extra parameters
if (mqtt_client.connect(clientId.c_str(),myConfig.mqtt_username,myConfig.mqtt_password)) {
Possibly look at the way tasmota does it? they have (for example)
tele/tasmota_id/LWT Online which reverts to
tele/tasmota_id/LWT Offline when no heartbeat / keepalive detected -- this allows Home Assistant to mark the sensor as unavailable (https://www.home-assistant.io/docs/mqtt/birth_will/ for docs)