public async Task <JsonResult> AssignAsync(Guid studentId, Guid semesterId)
        {
            var studentSemester = new StudentSemesterViewModel
            {
                StudentId  = studentId,
                SemesterId = semesterId
            };
            var result = await _studentService.AddStudentSemesterAsync(studentSemester);

            return(new JsonResult(result));
        }