Resolve "(CTTC) Resolve issue with common library and missing import"

Closes #297 (closed)

src/common/tools/grpc/Constraints.py

@@ -16,6 +16,7 @@
 # Ref: https://datatracker.ietf.org/doc/html/rfc8466
 
 
+import json
 from typing import Any, Dict, List, Optional, Tuple
 from common.proto.context_pb2 import Constraint, ConstraintActionEnum, EndPointId, QoSProfileId
 from common.tools.grpc.Tools import grpc_message_to_json_string