Set response_expires_at field to Payload (#129)

Co-authored-by: Mebin Abraham <[email protected]>

runner_benchmark/token_generator.py

@@ -1,7 +1,7 @@
 import os
 import time
 from uuid import uuid4
-
+from datetime import datetime, timedelta, timezone
 from sdc.crypto.encrypter import encrypt
 from sdc.crypto.key_store import KeyStore
 
@@ -76,7 +76,9 @@ def _get_payload_with_params(schema_name, schema_url=None, **extra_payload):
     payload_vars['iat'] = time.time()
     payload_vars['exp'] = payload_vars['iat'] + float(3600)  # one hour from now
     payload_vars['jti'] = str(uuid4())
-
+    payload_vars['response_expires_at'] = (
+        datetime.now(tz=timezone.utc) + timedelta(days=7)
+    ).isoformat()  # 7 days from now in ISO 8601 format
     for key, value in extra_payload.items():
         payload_vars[key] = value