1. Create a config file like such:
{
  "mqtt": {
    "host": ${SERVER_IP},
    "user": ${MQTT_USER},
    "password": ${MQTT_PASSWORD}
  }
}

2a. Put the config.json in /etc/light_groups/config.json to load by default
2b. Put the config.json in a volume that links it to /data/config.json in the docker container
2c. Put the config.json wherever and pass it as the first argument to the script
3. Publish a configuration json to light_groups/config. Example in test.json
4. ???
5. Profit?