public IActionResult AddCourseEnrollment(int crsId, int stdId)
        {
            if (_db.GetStudentById(stdId) == null && _db.GetCourseById(crsId) == null)
            {
                NotFound("Check Your Data");
            }

            else
            {
                Course EnrolledCourse = _db.AddCourseEnrollment(crsId, stdId);
                return(Ok(EnrolledCourse));
            }

            return(BadRequest());
        }