Decode the acceptcontent map (values keyed by schema property name)
into a typed struct T. Pairs with RequestContext.elicit!T, whose
requestedSchema is derived from the same T. Only meaningful for an
accept; on a decline/cancel (no content) this returns T.init, so
callers should branch on action first.
Decode the accept content map (values keyed by schema property name) into a typed struct T. Pairs with RequestContext.elicit!T, whose requestedSchema is derived from the same T. Only meaningful for an accept; on a decline/cancel (no content) this returns T.init, so callers should branch on action first.