public function addOwnerToGroup($email, $groupId)
    {
        $owner = $this->newOwnerEntry();

        $properties[] = $this->newProperty();
        $properties[0]->name = 'email';
        $properties[0]->value = $email;

        $owner->property = $properties;

        $uri  = self::APPS_BASE_FEED_URI . self::APPS_GROUP_PATH . '/';
        $uri .= $this->getDomain() . '/' . $groupId . '/owner';

        return $this->insertOwner($owner, $uri);
    }