public async Task Reserver(IDialogContext context, WitResult result)
        {
            var form = ReservationForm.ReadFromWit(result);

            if (string.IsNullOrWhiteSpace(form.RestaurantName) || !form.PeopleCount.HasValue || !form.ReservationDate.HasValue)
            {
                await context.PostAsync("Des informations sont manquantes");

                return;
            }

            await context.PostAsync($"Je vous ai réservé une table pour {form.PeopleCount.Value} chez {form.RestaurantName} à {form.ReservationDate.Value.ToString("HH\\hmm")} le {form.ReservationDate.Value.ToString("dd/MM/yyyy")}");
        }
        public async Task Reserver(IDialogContext context, WitResult result)
        {
            var form = ReservationForm.ReadFromWit(result);

            if (string.IsNullOrWhiteSpace(form.RestaurantName) || form.PeopleCount == 0 || form.ReservationDate == null)
            {
                var reservationForm = new FormDialog <ReservationForm>(form, ReservationForm.BuildForm, FormOptions.PromptInStart);
                context.Call(reservationForm, ResumeAfterReservationFormCompleted);

                return;
            }

            await ResumeReservation(context, form);
        }