Generate a JSON Schema (2020-12) fragment describing the D type T.
Validate a JSON value against a JSON Schema schema (a schema document of the kind produced by jsonSchemaOf).
A field type permitted in an elicitation form schema: a scalar (string / number / integer / boolean / enum), optionally wrapped in Nullable. The elicitation requestedSchema (SEP-1034/1330) is a flat object of such primitives — no nested objects or arrays.
True when T is a flat struct whose every field is an isElicitScalar, i.e. a valid type to derive an elicitation form requestedSchema from (via jsonSchemaOf!T). Used by RequestContext.elicit!T and InputRequest.elicitation!T to reject nested/array structs at compile time.