feat(ADM-018): completed feature

work/artifacts/F-022/documenter.md

@@ -0,0 +1,34 @@
+# Documenter — F-022 Checkout orchestrator with idempotency
+
+## Summary
+Checkout orchestrates cart -> pricing -> inventory -> promotions -> shipping -> orders -> reservation -> payment. It owns no business data and exposes a single endpoint with idempotency_key.
+
+## Public API notes
+
+| Route | Access | Result |
+|---|---|---|
+| POST /checkout | authenticated | Returns order summary, reservedVariantIds and payment intent reference |
+
+## Errors
+- `CHECKOUT_CART_EMPTY` — 409
+- `CHECKOUT_STOCK_UNAVAILABLE` — 409
+- `CHECKOUT_PRICE_MISSING` — 409
+- `CHECKOUT_PROMO_INVALID` — 422
+- `CHECKOUT_SHIPPING_ZONE_NOT_FOUND` — 422
+- `CHECKOUT_RESERVATION_FAILED` — 409
+- `CHECKOUT_IDEMPOTENCY_CONFLICT` — 409
+
+## Idempotency
+- `idempotencyKey` is required.
+- Reusing the same `(userId, idempotencyKey)` returns the existing order without re-reserving stock or creating a new payment intent.
+
+## Metrics
+- `checkout_success_total` increments on successful checkout.
+- `checkout_failure_total` increments on any 4xx/5xx checkout error.
+
+## Evidence
+- `work/artifacts/F-022/architect.md`
+- `work/artifacts/F-022/implementer.md`
+- `work/artifacts/F-022/reviewer.json`
+- `work/artifacts/F-022/security.json`
+- `work/artifacts/F-022/qa.json`