public function addMemberToGroup($recipientAddress, $groupId)
    {
        $member = $this->newMemberEntry();

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

        $member->property = $properties;

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

        return $this->insertMember($member, $uri);
    }