private void BookRoom(int roomId)
        {
            TimeSlotModel timeslot = new TimeSlotModel
            {
                Roomid   = roomId,
                Datetime = bookableDateTimes[comboBoxDates.SelectedIndex].ToShortDateString(),
                Timeslot = comboBoxTimeSlots.Items[comboBoxTimeSlots.SelectedIndex].ToString(),
                Booked   = true
            };

            SqliteDataAccess.BookTimeSlot(timeslot);

            LoadAvailability();
        }