Is it possible to install/access SSL for my Google App Engine app?

Since App Engine is so locked down I assume there is no way to setup an SSL certificate to allow credit card payments. In the absence of this, how is it possible to secure handle payments in an App Engine app?

http://code.google.com/appengine/docs/java/config/webxml.html#Secure_URLs says that

 <ssl-enabled>true</ssl-enabled>

can be set in your appengine-web.xml file with *.appspot.com subdommains. Google had a typo in their opening tag on that page, just FYI. For Google Apps you can't use HTTPS at all, but for appspot you can.

As far as using your own cert, you can't! For appspot, Google's cert is not signed for your web-app's specific domain so it will cause a browser pop-up, but if accepted the page will load.