MQTT Request-Response Interface for Nero

Description

Nero needs to be able to query the lap timer system for historical data via MQTT. The backend should subscribe to a Nero-published request topic and respond with aggregate lap data, enabling Nero to display summaries without polling the REST API.

Acceptance Criteria

• Nero can publish to a request topic to ask for lap summary data
• Backend responds with total lap count
• Backend responds with total driving time
• Backend responds with all individual lap times

Proposed Solution

Subscribe to a request topic (e.g. timers/lap/request). On message received, publish responses to a response topic (e.g. timers/lap/response) with a structured payload containing total_laps, total_time, and lap_times[]. Reference existing MQTT subscription patterns in scylla-server/src/. Test using an MQTT client to publish requests and verify responses.

Mocks

No response

Start by reviewing the existing MQTT subscription patterns in scylla-server/src and identify the backend entry point for handling lap data requests. Use an MQTT client to publish a request and verify the response. Done means Nero can receive total lap count, total driving time, and all individual lap times in the structured response.