Unavailable booking

Added

• Vietnam country code for SAW
• THH: check in/out time info
• Poplidays: skip properties with zero max_guest
• Common booking errors module Concierge::Errors::Booking
• THH: handle booking not available case in common manner

Fixed

• JTB: ignore units without availability calendar

Changed

• Refactor reading suppliers.yml, extract all logic in Concierge::SupplierConfig class