Add extra request parameters extra_query and extra_body (#500)

Added the possibility to pass `extra_query` and `extra_body` parameters
when sending a request.
In this implementation I added the attributes to `ModelSettings` as
suggested by @rm-openai in #487 .

I'll be happy to add some tests if you have any suggestions.

src/agents/model_settings.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from dataclasses import dataclass, fields, replace
 from typing import Literal
 
+from openai._types import Body, Query
 from openai.types.shared import Reasoning
 
 
@@ -58,6 +59,14 @@ class ModelSettings:
     """Whether to include usage chunk.
     Defaults to True if not provided."""
 
+    extra_query: Query | None = None
+    """Additional query fields to provide with the request.
+    Defaults to None if not provided."""
+
+    extra_body: Body | None = None
+    """Additional body fields to provide with the request.
+    Defaults to None if not provided."""
+
     def resolve(self, override: ModelSettings | None) -> ModelSettings:
         """Produce a new ModelSettings by overlaying any non-None values from the
         override on top of this instance."""

src/agents/models/openai_chatcompletions.py

@@ -540,6 +540,8 @@ class OpenAIChatCompletionsModel(Model):
             store=self._non_null_or_not_given(store),
             reasoning_effort=self._non_null_or_not_given(reasoning_effort),
             extra_headers=_HEADERS,
+            extra_query=model_settings.extra_query,
+            extra_body=model_settings.extra_body,
             metadata=self._non_null_or_not_given(model_settings.metadata),
         )
 

src/agents/models/openai_responses.py

@@ -245,6 +245,8 @@ class OpenAIResponsesModel(Model):
             parallel_tool_calls=parallel_tool_calls,
             stream=stream,
             extra_headers=_HEADERS,
+            extra_query=model_settings.extra_query,
+            extra_body=model_settings.extra_body,
             text=response_format,
             store=self._non_null_or_not_given(model_settings.store),
             reasoning=self._non_null_or_not_given(model_settings.reasoning),