Support 3D pivot table

[YosefSchwartz]

Thanks for the greatest ORM!

In my case, I have 3 tables that I need use one pivot table to connect them toghether.
I have User, that can have some Applications, and for each Application exist Permission.

So I have:
Users:
id, name
Application:
id, name
Permission:
id, name

and pivot table; users_applications_permissions:
id, user_id, application_id, permission_id.

I don't know how to implement it with the existing decorators, but if it does not exist, it can be very helpful.