Create a booking with an idempotency key so retries cannot double-book a guest.
curl -X POST https://api.tripistic.com/v1/bookings \
+ -H "Authorization: Bearer $TRIPISTIC_API_KEY" \
+ -H "Content-Type: application/json" \
+ -H "Idempotency-Key: 4f8c2a1e-9d33-4a11-b2c7-77c9a1e0f2b4"