public async Task <IActionResult> Approve(int id, bool students, bool teachers, bool advisers)
        {
            if (SchedulePlanExists(id))
            {
                SchedulePlan schedulePlan = await _context.SchedulePlans.FindAsync(id);

                String name = User.Identity.Name;
                User   user = await _userManager.FindByNameAsync(name);

                schedulePlan.Approve(user.SecondName + " " + user.FirstName[0] + "." + user.MiddleName?[0] +".", DateTime.Now);
                _context.Update(schedulePlan);
                await _context.SaveChangesAsync();

                await MailingAsync(id, students, teachers, advisers);

                return(RedirectToAction(nameof(Index)));
            }
            return(NotFound());
        }