Use issuer as subject (GoogleCloudPlatform#1343)

End Points: Use issuer as subject

Author: nownabe

endpoints/bookstore-grpc/jwt_token_gen.py

@@ -48,7 +48,7 @@ def generate_jwt(service_account_file, issuer, audiences):
         # swagger spec. It can be any string.
         'iss': issuer,
         # sub and email are mapped to the user id and email respectively.
-        'sub': '12345678',
+        'sub': issuer,
         'email': '[email protected]'
     }