refactor(api): scope uv to s2s-client and validate compatible responses

s2s-client/s2s_client/api/responses.py

@@ -0,0 +1,18 @@
+"""Validate service-owned response structure without rewriting the wire body."""
+
+from typing import Any
+
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel
+
+
+def validated_json_response(
+    content: Any,
+    model: type[BaseModel],
+    *,
+    status_code: int = 200,
+) -> JSONResponse:
+    model.model_validate(content)
+    # model_dump would insert defaults, potentially coerce values, and reorder
+    # fields. Keeping the original JSONResponse serialization is intentional.
+    return JSONResponse(content=content, status_code=status_code)