public async Task <IActionResult> AddCourse(int courseId)
{
var course = _data.GetFullCourse(courseId);
var userId = User.GetUserId();
var user = _userData.GetUserWithStats(userId);
user.CourseStatistics.Add(CreateStatisticsForCourse(course));
_userData.UpdateUser(user);
_userData.AddCourseToUser(course, user);
return(RedirectToAction("Details", "Course", new { id = courseId }));
}