Data Transfer Objects (DTOs) for the Fynd RPC HTTP API.
This crate contains only the wire-format types shared between the Fynd RPC server
(fynd-rpc) and its clients (fynd-client). It has no server-side infrastructure
dependencies (no actix-web, no server logic).
Enable the openapi feature to derive utoipa::ToSchema on all types for use in
API documentation generation.