OptionalallowOptionalcaseMatch the request's keys to the schema's ignoring case, as Go's
encoding/json does: { "NOMBRE": "Ana" } fills nombre. Nested objects
and arrays too. Needs a Zod object schema (it reads its shape).
OptionaldetailsThe details of a failed validation; default: the contract's, else 'flatten'.
Also accept form bodies (urlencoded and multipart). Default: JSON only.