Prepare a checkout's membership items
What It Does
Checkout preparation explains the coverage a purchase would provide without reserving it. Membership supplies eligibility, dates, units, grant plans and pricing context for Commerce.
The Flow
When Something Fails
A malformed envelope is a non-retryable contract failure; unexpected errors propagate for caller retry. Eligibility and configuration refusals produce coded item results. Approval-required is a supported answer and reserves nothing.