public IEnumerable <string> GetEmailListOfSoonToBeExpiredSubscription(int threshold)
{
var soonToExpire = subscriptionRepository.GetAll()
.Where(sub => sub.FixedContract && IsSubscriptionExpiringSoon(threshold, sub));
var userIdsWithExpiringSub = soonToExpire
.Where(sub => userRepository.GetById(sub.ClientId).Type == UserType.User)
.Select(sub => sub.ClientId);
var emailsOfUserWithExpiringSub = userIdsWithExpiringSub.Select(id => loginRepository.ByUserId(id).Email);
return(emailsOfUserWithExpiringSub.ToList());
}