Getting the Authentication username column

I need to get the auth username that is used by the app for authentication from a User object. The column used for authentication is changing based on system/environment (can be email or username or some other column)

Is it a good idea to put that as a public property in the User model (I will add username_column to auth.php):

class User extends Authenticatable 
{
    public $username_column = config('auth.username_column')
}

or as a getter in the User model:

class User extends Authenticatable 
{
    public function getUsernameColumn()
    {
        return config('auth.username_column');
    }
}

Or something else?

Edit: For more context, I get the User object in a Illuminate\Auth\Events\Login event's Listener:

public function handle(Object $event)
{
    // $user = $event->user
}

and I want to get the value of the column that is used by the app to authenticate the user (and it can change - sometimes username, sometimes email, and sometimes other custom column)

In my opinion, you shouldn't put your column name in the configuration. An authentication identifier isn't something that we change regularly, so don't put the identifier in the public property. Laravel Authenticatable has provided some methods to implement your custom column.

On the controller that handles the authentication or login process, inside the AuthenticatesUsers trait, there is a method named username() as the column name that will be used for the Auth::attempt() process

public class AuthController extends Controller
{
    use AuthenticatesUsers;

    public function username()
    {
        return 'username_column'
    }
}

When the user has been authenticated, 2 options can be used:

Option 1:
We can override the Authenticatable trait to get the identifier and the value.

• getAuthIdentifierName() will return the name of the username column
• getAuthIdentifier() will return the value of the username column

class User extends Authenticatable
{
    public function getAuthIdentifierName()
    {
        return `username_column`
    }
}

/* Get the Auth username */
Auth::user()->getAuthIdentifier();

Option 2:
You can call using the Auth identifier without overriding the authenticable methods.

User::find(Auth::id())->username_column;

More information:

• Authenticatable