Sage: Make multiple bookings

booking_sage_multiple.ex

def book_trip(attrs) do
  with {:ok, exchange_rates} <- BillingAPI.fetch_currency_exchange_rates(attrs),
       {:ok, card_authorization} <- BillingAPI.authorize_card(exchange_rates, attrs),
       {:booking, {:ok, hotel_booking}, _} <- {:booking, HotelsBookingAPI.book_hotel(attrs), []},
       {:booking, {:ok, car_booking}, _} <- {:booking, CarsBookingAPI.book_hotel(attrs), [hotel_booking]},
       {:booking, {:ok, flight_booking}, _} <- {:booking, FlightsBookingAPI.book_hotel(attrs), [hotel_booking, car_booking]},
       :ok <- Mailer.send_email_confirmation(card_authorization, hotel_booking, attrs),
       {:charge, {:ok, charge}, _} <- {:charge, BillingAPI.charge_card(card_authorization), [...]} do
    {:ok, %{charge: charge, bookings: [hotel_booking, car_booking, flight_booking]}}
  else
    {:charge, {:error, reason], bookings} ->
      :ok = send_excuse_email(authorization)
      :ok = cancel_bookings(bookings)
      {:error, reason}

    {:booking, {:error, reason}, bookings} ->
      :ok = cancel_bookings(bookings)
      {:error, reason}
  end
end