private Task HandleResponseMessage(AzureServiceBusMessage message, CancellationToken cancellationToken)
        {
            if (message.UserProperties.TryGetValue(RequestMessageIdentifierUserPropertyKey, out var requestMessageIdentifier))
            {
                var responseMessageKey = requestMessageIdentifier?.ToString();

                if (responseMessageKey.IsNullOrEmpty())
                {
                    throw new InvalidOperationException("The response message did not contain a request identifier.");
                }

                if (OutstandingResponseKeys.Contains(responseMessageKey))
                {
                    OutstandingResponseKeys.Remove(responseMessageKey);

                    if (ResponseMessageDictionary.TryAdd(responseMessageKey, message))
                    {
                        return(Task.CompletedTask);
                    }
                }
                else
                {
                    // The response is intended for another client manager.
                    return(Task.CompletedTask);
                }
            }

            throw new InvalidOperationException("The response subscriber received multiple responses or the system state is corrupt.");
        }
 internal void AddOutstandingRequest(Guid requestMessageIdentifier) => OutstandingResponseKeys.Add(requestMessageIdentifier.ToSerializedString());