Add `--mqtt.password-file` flag and `MQTT_PASSWORD_FILE` env var to allow reading the MQTT password from a file (e.g. Docker secrets). When set, the file contents overrides the --mqtt.password value. Addresses diebietse/invertergui#46
Add `--mqtt.password-file` flag and `MQTT_PASSWORD_FILE` env var to allow reading the MQTT password from a file (e.g. Docker secrets). When set, the file contents overrides the --mqtt.password value. Addresses diebietse/invertergui#46