feat(gateway): typed DTO contract for HTTP responses and OpenAPI schema

README.md

@@ -98,7 +98,7 @@ Beyond faults, medkit exposes the full ROS 2 graph through REST:
 | **Software Updates** | Async prepare/execute lifecycle with pluggable backends |
 | **Authentication** | JWT-based RBAC (viewer, operator, configurator, admin) |
 | **Logs** | Log entries and configuration |
-| **Docs** | OpenAPI 3.1.0 spec and Swagger UI at `/api/v1/docs` |
+| **Docs** | OpenAPI 3.1.0 spec and Swagger UI at `/api/v1/docs` - schemas are generated from typed C++ structs so the spec always matches the wire format |
 
 On the [roadmap](https://selfpatch.github.io/ros2_medkit/roadmap.html): entity lifecycle control, mode management, communication logs.
 

docs/tutorials/openapi.rst

@@ -77,6 +77,28 @@ When disabled, all ``/docs`` endpoints return HTTP 501.
 
 See :doc:`/config/server` for the full parameter reference.
 
+How Schemas Are Generated
+--------------------------
+
+The ``components/schemas`` object in every ``/docs`` response is generated
+automatically from the DTO registry. Each response and request type in the
+gateway is declared as a plain C++ struct with a ``constexpr dto_fields<T>``
+descriptor tuple. The ``SchemaWriter<T>`` visitor folds over this tuple at
+compile time to produce the OpenAPI JSON Schema entry, and the
+``AllDtos`` registry in ``dto/registry.hpp`` lists every named type so that
+``collect_component_schemas()`` can populate the full schema map without
+any hand-written schema factories.
+
+The same descriptor is used for serialization (``JsonWriter<T>``) and
+request-body validation (``JsonReader<T>``), so the wire shape and the
+published schema are always derived from the same source. Genuinely dynamic
+payloads - such as live ROS 2 message data and free-form fault environment
+records - are typed as ``nlohmann::json`` members and appear in the schema
+as unconstrained objects (``{}``).
+
+For the full design of the DTO contract layer, see
+:doc:`/design/ros2_medkit_gateway/dto_contract`.
+
 See Also
 --------
 

src/ros2_medkit_gateway/CMakeLists.txt

@@ -631,9 +631,9 @@ if(BUILD_TESTING)
   target_link_libraries(test_handler_context gateway_ros2)
   medkit_set_test_domain(test_handler_context)
 
-  # Add x-medkit extension tests
-  ament_add_gtest(test_x_medkit test/test_x_medkit.cpp)
-  target_link_libraries(test_x_medkit gateway_ros2)
+  # DTO contract core (pure C++17, no ROS node)
+  ament_add_gtest(test_dto_contract test/test_dto_contract.cpp)
+  target_link_libraries(test_dto_contract gateway_core)
 
   # Add rate limiter tests
   ament_add_gtest(test_rate_limiter test/test_rate_limiter.cpp)
@@ -929,7 +929,6 @@ if(BUILD_TESTING)
       test_manifest_manager
       test_capability_builder
       test_handler_context
-      test_x_medkit
       test_rate_limiter
       test_auth_config
       test_data_access_manager