The API Contract

Everything real in PawWalk lives on the backend

The walkers, your bookings, your login — none of it is hardcoded in the app. It all comes from a Python (FastAPI) server the app talks to over HTTP. Up to now you've worked with Walker and Booking as Kotlin types sitting in memory. This module is about how those values actually get into the app: a request goes out, JSON comes back.

The agreement about exactly what JSON the backend sends and expects lives in one file: docs/API-CONTRACT.md. Every Kotlin type you've built in this course mirrors a shape written down there. When in doubt about a field name or an endpoint path, that file is the source of truth — not memory, not guessing.