feat: support for customizing “tool_choice” in OpenAI

The ModelSettings class uses a TypedDict as its underlying type, providing
flexibility to add options beyond the predefined attributes.

Before generating chat completions, the code now checks if tool_choice is set
in ModelSettings and applies it accordingly.

Fixes: #224
Signed-off-by: Sébastien Han <seb@redhat.com>

pydantic_ai_slim/pydantic_ai/models/openai.py

@@ -186,7 +186,9 @@ async def _completions_create(
         self, messages: list[ModelMessage], stream: bool, model_settings: OpenAIModelSettings
     ) -> chat.ChatCompletion | AsyncStream[ChatCompletionChunk]:
         # standalone function to make it easier to override
-        if not self.tools:
+        if tool_choice := model_settings.get('tool_choice'):
+            pass
+        elif not self.tools:
             tool_choice: Literal['none', 'required', 'auto'] | None = None
         elif not self.allow_text_result:
             tool_choice = 'required'