Python: OpenAI responses client (#239)

* Responses client WIP

* add responses class

* fix typing errors

* move test

* streaming responses, structured outputs

* tests

* Update python/packages/main/tests/openai/test_openai_responses_client.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* pr comments

* fix override import

* fix mypy

* add missing function override

* PR comments

* add docstrings

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

python/samples/getting_started/chat_client/openai_responses_client.py

@@ -0,0 +1,36 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+import asyncio
+from random import randint
+from typing import Annotated
+
+from agent_framework.openai import OpenAIResponsesClient
+from pydantic import Field
+
+
+def get_weather(
+    location: Annotated[str, Field(description="The location to get the weather for.")],
+) -> str:
+    """Get the weather for a given location."""
+    conditions = ["sunny", "cloudy", "rainy", "stormy"]
+    return f"The weather in {location} is {conditions[randint(0, 3)]} with a high of {randint(10, 30)}°C."
+
+
+async def main() -> None:
+    client = OpenAIResponsesClient(ai_model_id="gpt-4o-mini")
+    message = "What's the weather in Amsterdam and in Paris?"
+    stream = False
+    print(f"User: {message}")
+    if stream:
+        print("Assistant: ", end="")
+        async for chunk in client.get_streaming_response(message, tools=get_weather):
+            if str(chunk):
+                print(str(chunk), end="")
+        print("")
+    else:
+        response = await client.get_response(message, tools=get_weather)
+        print(f"Assistant: {response}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())