title: MQTT topic transform in Mosquitto
body: <p>I'm working on integrating a Shelly sensor(<a href="https://shelly.cloud/" rel="nofollow noreferrer">https://shelly.cloud/</a>) into an existed IoT system FIWARE(<a href="https://www.fiware.org/" rel="nofollow noreferrer">https://www.fiware.org/</a>). The sensor can publish the monitoring data via MQTT with JSON payload.</p>
  <p>Shelly sensor published the data at topic <strong>{SHELLY_ID}/events/rpc</strong>, but the FIWARE can only subscribe on topic <strong>/json/{{api-key}}/{{device-id}}/attrs</strong>. The topic of publication and subscription are different now. In our application, we use <strong>Mosquitto</strong> as an MQTT broker, is it possible to do the topic transform in Mosquitto broker?</p>
  <p>I think Mosquitto has full knowledge of topics and can do the topic mapping and transformation easily. Does anyone have an idea or information for this? I think it's much easier than to re-build and customize the FIWARE system.</p>