public async Task <IActionResult> AddWorkoutToDay([FromBody] WorkoutDayForm data)
        {
            try
            {
                if (!ModelState.IsValid || data == null)
                {
                    return(BadRequest());
                }

                var day = await _context.TrainingDays.SingleOrDefaultAsync(d => d.Id == data.DayId);

                var workout = await _context.Workouts.SingleOrDefaultAsync(w => w.Id == data.WorkoutId);

                var workoutDay = new TrainingDayWorkout {
                    TrainingDay = day, TrainingDayId = day.Id, Workout = workout, WorkoutId = workout.Id
                };
                day.TrainingDayWorkouts.Add(workoutDay);
                await _context.SaveChangesAsync();

                return(Ok(data));
            }
            catch (Exception e)
            {
                return(StatusCode(500));
            }
        }
        public async Task <IActionResult> RemoveWorkoutFromDay([FromBody] WorkoutDayForm data)
        {
            try
            {
                if (!ModelState.IsValid)
                {
                    return(BadRequest());
                }

                var day = await _context.TrainingDays.Include(d => d.TrainingDayWorkouts).SingleOrDefaultAsync(d => d.Id == data.DayId);

                var dayWorkout = day.TrainingDayWorkouts.FirstOrDefault(w => w.WorkoutId == data.WorkoutId);
                day.TrainingDayWorkouts.Remove(dayWorkout);
                await _context.SaveChangesAsync();

                return(Ok(data));
            }
            catch (Exception e)
            {
                return(StatusCode(500));
            }
        }