I've created a simple webapp, how do I limit access to a particular group?

I've added WiPhA to our 10.7.2 Lion Server to share photos with windows, mac and iDevice users on our intranet. I installed the application to /Library/Server/Web/Data/Sites/CustomSitesDefault/wipha/ using echo /Library/Server/Web/Data/Sites/CustomSitesDefault > /tmp/wiphadest before installing

I then created a simple webapp to add an alias to our default website:

1. In /etc/apache2 create file httpd_wipha.conf

# Config file for linking the wiPhA iPhoto sharing manager to MacOSX Server Web Server.

#

Alias /photos/ "/Library/Server/Web/Data/Sites/CustomSitesDefault/wipha/"

<Directory "/Library/Server/Web/Data/Sites/CustomSitesDefault/wipha/">

Options FollowSymLinks MultiViews Indexes

AllowOverride All

Order allow,deny

Allow from all

</Directory>

2. chown root:wheel httpd_wipha.conf

3. In /etc/apache2/webapps create file com.anynameyoulike.wipha.plist

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<!-- See man pages for webapp.plist(5) and webappctl(8) for information about this example webapp.plist -->

<plist version="1.0">

<dict>

<key>includeFiles</key>

<array> <!-- Include files are activated in virtual host when webapp is started -->

<string>/etc/apache2/httpd_wipha.conf</string>

</array>

<key>launchKeys</key>

<array> <!-- Launchd plists in /System/Library/LaunchDaemons are loaded when webapp is started -->

<!-- <string>com.example.mywebapp</string> -->

</array>

<key>name</key>

<string>com.splatcooking.wipha</string>

<key>sslPolicy</key> <!-- Determines webapp SSL behavior -->

<integer>4</integer> <!-- 0: default, UseSSLWhenEnabled -->

<!-- 1: UseSSLAlways -->

<!-- 2: UseSSLOnlyWhenCertificateIsTrustable -->

<!-- 3: UseSSLNever -->

<!-- 4: UseSSLAndNonSSL -->

</dict>

</plist>

4. Start the webapp sudo webappctl start com.anynameyoulike.wipha "*"

5. Browse to http/yourdefaultwebsite/photos/

6. Setup WiPha to access your iPhoto library

OK, that was how I did it (which means that the WiPhA install should survive upgrades to OSX). What I want to do now is learn how to authenticate WiPhA to Open Directory so I can give single sign on via the Wiki. Any ideas or pointers welcome.