refactor: pass external_trace_id to message trace (#23089)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/controllers/service_api/app/completion.py

@@ -47,6 +47,9 @@ class CompletionApi(Resource):
         parser.add_argument("retriever_from", type=str, required=False, default="dev", location="json")
 
         args = parser.parse_args()
+        external_trace_id = get_external_trace_id(request)
+        if external_trace_id:
+            args["external_trace_id"] = external_trace_id
 
         streaming = args["response_mode"] == "streaming"