use jumper423\LaravelTrait\Filter;

class Post{
    use Filter;
    
    protected $filterColumns = [
        'user_name' => 'user.first.name'
    ];
}

$posts = Post::join('users', 'users.id', '=', 'posts.user_id')
    ->filter([
        [
            'name' => 'user_name'
            'value' => 'Вася'
        ]
    ])->get();