Returns a cost preview for a potential checkout without creating an order or charging the member. Provide either memberships/fees or a booking, but not both. A discount code can be included to see its effect on pricing.

Memberships/Fees flow: Calculates the order total based on the selected plans, fees, and the member's billing context (billing flow, currency, tax settings). Returns line items, subtotal, total, tax breakdown, and any applicable processing fees or discounts.

Booking flow: Returns a summary of the booking request including resource availability pricing, per-date fee breakdown with credits and coins applied, and the cancellation policy that would apply to the booking.

Required scopes: flex.billing.checkout.create