Couple additions to AuthenticatorInterface

[FrancoisChaumont]

Hey all,

I thought it'd be helpful to suggest adding the following to CodeIgniter\Shield\Authentication\AuthenticatorInterface:

/**
 * Starts login process
 */
public function startLogin(User $user): void;

/**
 * Completes login process
 */
public function completeLogin(User $user): void;

Useful for code auto-completion.

Use-case: dynamically log in a user when not going through the usual login process (login page, credentials verification, 2FA...).

That's it. Thanks

PS: I couldn't find a way to easily extend AuthenticatorInterface so I'm posting it here.