Show to customer that the voucher is already reserved

[ElenaBelyavskaya]

As a mobile user, when I reserved a voucher and get back to it
I want to easily see that the voucher is already reserved by myself and be able to finalize the purchase
In order to avoid confusion or errors when trying to reserve another instance of the same voucher again.

(TBD

• Show in vouchers details instead of just Buy button, smth like "Complete purchase"
• Mark reserved vouchers among the offers
  ...)