Sage: Booking Happy-Case

booking_sage.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),
       {:ok, hotel_booking} <- HotelBookingAPI.book_hotel(attrs),
       :ok <- Mailer.send_email_confirmation(card_authorization, hotel_booking, attrs),
       {:ok, charge} <- BillingAPI.charge_card(card_authorization) do
    {:ok, %{charge: charge, bookings: [hotel_booking]}}
  end
end