public ActionResult DeleteStudent(string studentId)
        {
            if (!_repository.StudentExists(studentId))
            {
                return(NotFound());
            }

            var studentFromRepo = _repository.GetStudent(studentId);

            if (studentFromRepo == null)
            {
                return(NotFound());
            }
            _repository.DeleteStudent(studentFromRepo);

            return(NoContent());
        }