[serving] fix pydantic compatibility

Author: imoneoi

ochat/serving/openai_api_server.py

@@ -67,7 +67,7 @@ def log_request(created_time: int, request: openai_api_protocol.ChatCompletionRe
             time=created_time,
             request=request,
             outputs=[o.text for o in output.outputs]
-        ).json(exclude_unset=True, ensure_ascii=False))
+        ).model_dump_json(exclude_unset=True))
 
 
 def create_error_response(status_code: HTTPStatus,
@@ -206,7 +206,7 @@ def create_stream_response_json(
             model=model_name,
         )
 
-        return response.json(exclude_unset=True, ensure_ascii=False)
+        return response.model_dump_json(exclude_unset=True)
 
     async def completion_stream_generator() -> AsyncGenerator[str, None]:
         # First chunk with role
@@ -220,7 +220,7 @@ async def completion_stream_generator() -> AsyncGenerator[str, None]:
                                                                      choices=[choice_data],
                                                                      model=model_name)
 
-            yield f"data: {chunk.json(exclude_unset=True, ensure_ascii=False)}\n\n"
+            yield f"data: {chunk.model_dump_json(exclude_unset=True)}\n\n"
 
         previous_texts = [""] * request.n
         previous_num_tokens = [0] * request.n