protected function validate(array $data = array())
    {
        $id = auth()->user()->id;
        if (empty($data)) {
            return false;
        }
        if ((int) array_get($data, 'secondary_user_id') !== $id) {
            return false;
        }

        $primary = array_get($data, 'primary_user_id');
        if ($primary === null) {
            return false;
        }
        return true;
    }