message: fix: Force using JSON payload when HassDiscovery is enabled
diff: v-model="gateway.payloadType"
  label="Payload type"
  required
  + :rules="[validPayload]"
  :items="py_types"
  ></v-select>
  </v-flex>
  @@ -477,6 +478,9 @@ export default {
  (this.mqtt.auth && !!this.mqtt.username) || 'This field is required.'
  )
  },
  + validPayload () {
  + return (!this.gateway.hassDiscovery || this.gateway.payloadType !== 2) || 'Hass discovery doesn\'t works with this payload type'
  + },
  requiredPassword () {
  return (
  (this.mqtt.auth && !!this.mqtt.password) || 'This field is required.'
  