Routers

One file per resource

app/main.py doesn't hold every route — that would be a repeat of Flask's giant app.py from module 19. Instead the real backend keeps one file per resource under app/routers/: walkers.py, bookings.py, payments.py, auth.py, and more. Each file builds its own APIRouter and gets wired into the app once, in main.py.

This is the exact same instinct as Flask's blueprints (module 19): a mini app for one resource's routes, defined in its own file, then registered onto the main app. APIRouter is FastAPI's blueprint — same idea, typed.