Add emitted timestamp for logging (#450)

* add timestamp

* change to utc

Author: tiffzhao5

model-engine/model_engine_server/inference/post_inference_hooks.py

@@ -1,7 +1,9 @@
 import json
 from abc import ABC, abstractmethod
+from datetime import datetime
 from typing import Any, Dict, List, Optional, Union
 
+import pytz
 import requests
 from fastapi.responses import JSONResponse
 from model_engine_server.common.constants import (
@@ -122,6 +124,7 @@ def handle(
             return
         response["task_id"] = task_id
         data_record = {
+            "EMITTED_AT": datetime.now(pytz.timezone("UTC")).strftime("%Y-%m-%dT%H:%M:%S"),
             "REQUEST_BODY": request_payload.json(),
             "RESPONSE_BODY": response,
             "ENDPOINT_ID": self._endpoint_id,