private bool CheckPseudoUnique(TrelloContext context)
        {
            var users = context.Users.SingleOrDefault(
                u => u.Pseudo == Pseudo && u.Id != Id);

            return(users == null);
        }
        private bool CheckEmailUnique(TrelloContext context)
        {
            var users = context.Users.SingleOrDefault(
                u => u.Email == Email && u.Id != Id);

            return(users == null);
        }