public IActionResult AllByUser(string id)
        {
            AllCoursesByUserListViewModel viewModel = new AllCoursesByUserListViewModel
            {
                Courses = this.coursesService.GetAllByUser <AllCoursesByUserViewModel>(id),
            };

            return(this.View(viewModel));
        }
        public async Task <IActionResult> AllByCurrentUser()
        {
            ApplicationUser user = await this.userManager.GetUserAsync(this.User);

            AllCoursesByUserListViewModel viewModel = new AllCoursesByUserListViewModel
            {
                Courses = this.coursesService.GetAllByUser <AllCoursesByUserViewModel>(user.Id),
            };

            return(this.View(viewModel));
        }