Python: Fix OpenAIEmbeddingClient to use AsyncOpenAI for /openai/v1 endpoints (#5137)

* Fix OpenAIEmbeddingClient with /openai/v1 endpoint (#5068)

When base_url ends with /openai/v1/ and a credential is provided,
load_openai_service_settings was creating an AsyncAzureOpenAI client.
The Azure SDK rewrites deployment-based endpoints (including /embeddings)
by inserting /deployments/{model}/ into the URL, producing 404s on the
OpenAI-compatible /openai/v1 endpoint.

Use AsyncOpenAI instead of AsyncAzureOpenAI when the resolved base_url
targets /openai/v1, converting the Azure token provider to an async
api_key callable. The responses_mode path is unaffected because the
Responses API (/responses) is not in the SDK's rewrite list.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Python: Fix OpenAIEmbeddingClient to use AsyncOpenAI for /openai/v1 endpoints

Fixes #5068

* Address review feedback: improve test coverage and remove unrelated changes

- Revert unrelated formatting change in test_a2a_agent.py
- Fix test_init_with_openai_v1_base_url_and_api_key_uses_openai_client to
  exercise the Azure settings path (via AZURE_OPENAI_BASE_URL env var)
  instead of the plain OpenAI path, covering the elif api_key branch
- Add _ensure_async_token_provider unit tests for both sync and async
  token providers

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback for #5068: Python: [Bug]: `OpenAIEmbeddingClient` does not work with `/openai/v1` endpoint

---------

Co-authored-by: MAF Dashboard Bot <maf-dashboard-bot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Evan Mattson <35585003+moonbox3@users.noreply.github.com>

python/packages/openai/tests/openai/test_openai_shared.py

@@ -8,7 +8,11 @@ import pytest
 from azure.core.credentials import TokenCredential
 from azure.core.credentials_async import AsyncTokenCredential
 
-from agent_framework_openai._shared import AZURE_OPENAI_TOKEN_SCOPE, _resolve_azure_credential_to_token_provider
+from agent_framework_openai._shared import (
+    AZURE_OPENAI_TOKEN_SCOPE,
+    _ensure_async_token_provider,
+    _resolve_azure_credential_to_token_provider,
+)
 
 
 class _AsyncTokenCredentialStub(AsyncTokenCredential):
@@ -52,3 +56,23 @@ def test_resolve_azure_callable_token_provider_passthrough() -> None:
 def test_resolve_azure_invalid_credential_raises() -> None:
     with pytest.raises(ValueError, match="credential"):
         _resolve_azure_credential_to_token_provider(object())  # type: ignore[arg-type]
+
+
+async def test_ensure_async_token_provider_wraps_sync_provider() -> None:
+    def sync_provider() -> str:
+        return "sync-token"
+
+    wrapper = _ensure_async_token_provider(sync_provider)
+    result = await wrapper()
+
+    assert result == "sync-token"
+
+
+async def test_ensure_async_token_provider_wraps_async_provider() -> None:
+    async def async_provider() -> str:
+        return "async-token"
+
+    wrapper = _ensure_async_token_provider(async_provider)
+    result = await wrapper()
+
+    assert result == "async-token"