feat: Add headers to VLLM Passthrough requests [Log success Events] (#16532)

Author: LucasSugi

litellm/proxy/pass_through_endpoints/pass_through_endpoints.py

@@ -521,6 +521,7 @@ def _init_kwargs_for_pass_through_endpoint(
                     "url": str(request.url),
                     "method": request.method,
                     "body": copy.copy(_parsed_body),  # use copy instead of deepcopy
+                    "headers": request.headers,
                 },
             },
             "call_type": "pass_through_endpoint",