integrate convious's rest api for cart-based ticket checkout on attractions

Steps

1. authenticate by POSTing client_id, client_secret, and grant_type=client_credentials (application/x-www-form-urlencoded) to https://identity.convious.com/oauth/token/ to obtain a Bearer access_token, then send it as an Authorization: Bearer header on all subsequent API calls
2. look up products and categories via GET https://api.convious.com/api/v1/products/ and GET .../categories/ to find productId and categoryId values, and check timeslot/day availability via the products or accounts availability endpoints
3. create a cart with POST https://api.convious.com/api/v1/accounts/<account_slug>/carts/, supplying categoryId, eventDate/startTime/endTime, and items (productId + amount); this reserves inventory for a limited time and can be updated (PATCH) or removed (DELETE)
4. optionally attach real pricing by first calling the Pricing API to obtain a pricingToken, then include it on cart creation/update so the cart reflects actual prices instead of defaulting to 0
5. convert the cart into a paid order with POST https://api.convious.com/api/v1/accounts/<account_slug>/bookings/, passing cartId and customer details — payment itself is handled outside Convious by the integrator
6. poll or sync orders via GET https://api.convious.com/api/v1/orders/ (filterable by from_updated_at) or cancel a completed order with POST https://api.convious.com/api/v1/orders/<order_id>/status/ (status: cancelled)