Auth & keys

Authorization: Bearer tl_test_<prefix>.<secret>
Authorization: Bearer tl_live_<prefix>.<secret>

Secret is shown once at creation and stored hashed.

Test vs live

tl_test_* for integration; tl_live_* for production. Environments are isolated.

Idempotency

Idempotency-Key: order_847291-create

Required for create and finalize to safely retry.