AppServiceProvider.php

<?php

use Illuminate\Contracts\Auth\Authenticatable;
use Illuminate\Support\Facades\Auth;
use Illuminate\Support\Facades\Gate;

Auth::macro('shadow', function ($user = null) {
    $ability = 'shadowLogin';
    $key = 'shadow.user.id';
    
    switch (true) {
        case is_callable($user):
            Gate::define($ability, $user);

            return null;
        case $user instanceof Authenticatable:
            if (Gate::allows($ability)) {
                session()->flush();
                session()->put($key, auth()->id());

                auth()->login($user);
            }

            return null;
        case $user === false:
            if ($id = session()->pull($key)) {
                session()->flush();
                auth()->loginUsingId($id);
            }

            return null;
        default:
            return Users::find(
                session()->get($key)
            );
    }
});