Invoice payment via Privat24 application

Added the ability to quickly pay an invoice through the Privat24 application. To do this, on the payment page, you need to select from the list the phone number that is used in the Privat24 application and click "Get". After that, a notification about payment confirmation will be displayed in the Privat24 application. You need to open it, select a card for payment and click "Confirm". A more detailed description is provided in wiki.