// Delete all WebHooks of a User
        public override async Task DeleteAllWebHooksAsync(string user)
        {
            if (user == null)
            {
                throw new ArgumentNullException(nameof(user));
            }

            user = NormalizeKey(user);

            try
            {
                await _webHookRepository.DeleteMany <Registration>(user);
            }
            catch (Exception ex)
            {
                var message = string.Format(CultureInfo.CurrentCulture, Constants.Constants.OperationFailed, "DeleteAll", ex.Message);
                _logger.Error(message, ex);
                throw new InvalidOperationException(message, ex);
            }
        }