public void ApproveDelegate(int delegateId, int centreId)
        {
            var delegateUser = userDataService.GetDelegateUserById(delegateId);

            if (delegateUser == null || delegateUser.CentreId != centreId)
            {
                throw new UserAccountNotFoundException(
                          $"Delegate user id {delegateId} not found at centre id {centreId}."
                          );
            }

            if (delegateUser.Approved)
            {
                logger.LogWarning($"Delegate user id {delegateId} already approved.");
            }
            else
            {
                userDataService.ApproveDelegateUsers(delegateUser.Id);

                SendDelegateApprovalEmails(delegateUser);
            }
        }