test(test_embedding.py): add test for passing extra headers via embedding

tests/local_testing/test_embedding.py

@@ -1080,3 +1080,20 @@ def test_cohere_img_embeddings(input, input_type):
         assert response.usage.prompt_tokens_details.image_tokens > 0
     else:
         assert response.usage.prompt_tokens_details.text_tokens > 0
+
+
+def test_embedding_with_extra_headers():
+    input = ["hello world"]
+    from litellm.llms.custom_httpx.http_handler import HTTPHandler
+
+    client = HTTPHandler()
+
+    with patch.object(client, "post") as mock_post:
+        embedding(
+            model="cohere/embed-english-v3.0",
+            input=input,
+            extra_headers={"my-test-param": "hello-world"},
+            client=client,
+        )
+
+        assert "my-test-param" in mock_post.call_args.kwargs["headers"]