Lab: Build BrightCart's callable returns service

Module 10 · Lab · About 75 minutes · Needs: lessons 1 to 5 of this module (FastAPI fundamentals, advanced FastAPI, auth, architecture, testing)

What you are building

This lab joins the five lessons into Module 10's piece of BrightCart: a web service other systems can call. Dev's ticket system, the chat widget and Priya's agents reach the same returns rules over HTTP. The service is a package on disk: checked settings, a ReturnService over SQLite, JWT login with two roles, four routes, a request-id middleware, health checks and a pytest suite. The running example is Aisha Rahman's order 6150, GlowLine bulbs delivered on 4 October 2026, five days before the course date. The model is a fake until the last step.