Add an optional checkbox to include a Security Deposit (Kaution)

Please add a built-in checkbox option to configure and apply a refundable security deposit (Kaution) per room type and booking. Currently, hoteliers have to rely on standard service products, which cannot be quickly toggled on/off during manual reservations and lack dedicated deposit tracking. Providing a simple toggle to enable or waive the deposit—along with separate refund handling upon checkout—would make front-desk operations much faster and cleaner.