Few years ago, I integrated picketlink
SAML with Google-apps . The docs is here
https://docs.jboss.org/author/display/PLINK/Picketlink+as+IDP,+Google+Apps+as+SP
.
The docs may be outdated, but hopefully some points are still
valid, especially for Google-apps domain setup (really not 100%
sure). Note that Keycloak SAML implementation is based on
Picketlink impl, so hopefully it should work.
You're right that we didn't test it (at least I am not aware). If
you or someone else from the community is able to successfully
integrate Keycloak with 3rd party providers like Google Apps,
Salesforce, Shiboleth etc, it will be cool if you can create the
blog or wiki somewhere. We can then backport to our docs or at
least link it from our blog, so other community people can see it.
Marek