Some fields missing in PreferenceItemRequest

[SandroMoretti]

Hello, I'm following mercado pago documentation: https://www.mercadopago.com.br/developers/pt/docs/checkout-pro/checkout-customization/user-interface/redirection

And there some fields that is missed in this api, that is beeing showed in main docs.

An example is backUrls:

but in code of this repository don't have backUrls in this class:

The same happen with the fields to exclude some payment types.

I'm using 2.1.7 version.
This fields was removed in some point? Have some way to remove payments type in current version?

Thank you.