I currently have a User Template that has a has_one relationship with Customer .
In the customer tables I have the CPF field that the user informs when to register.
I need to implement a login where the user inputs the e-mail or CPF to log in to the system.
The Devise documentation has an example of how to resolve this. It uses username or e-mail to exemplify, but easily adapts to CPF or e-mail . Take a look here is a somewhat laborious process, so I've put the link to you from a strong secure :).
So, to adapt to your case I think you'll have to change the behavior of find_for_database_authentication where you'll get CPF in the Customer table.
