Challenge 2: Add an Override File for Local Development — Possible Solution
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# docker-compose.override.yml
services:
  api:
    volumes:
      - .:/home/appuser/app
    environment:
      NODE_ENV: development

WHY THIS WORKS AS AN ANSWER
------------------------------
docker-compose.override.yml is picked up AUTOMATICALLY by Compose
whenever it sits alongside the base docker-compose.yml — no explicit
-f flag needed for local development, exactly the override-file
mechanism Chapter 3 introduced.

The volumes entry adds a BIND MOUNT (Chapter 5) mapping the current
host directory (.) into the exact path the api container's Dockerfile
already uses as its working directory
(/home/appuser/app, matching Step 1's WORKDIR) — so edits made on the
host are immediately reflected inside the running container, enabling
live-reload during development, without needing to rebuild the image
for every source change.

Crucially, this override file does NOT touch or duplicate anything
from the base docker-compose.yml — it only ADDS the volumes and
environment keys on top of the api service already defined there,
exactly the additive-merge behavior Chapter 3 described for keys like
environment (as opposed to keys like command, which would replace
rather than merge). Running plain `docker compose up` locally
automatically picks up this override; a production deployment that
explicitly specifies only the base file (or a different override)
never sees this local-only bind mount at all.