Fixes for tests that are failing on keycloak version >= 9

[tomrutsaert]

• fix issue 291: creating resource keycloak_user with federated_identity fails with keycloak >= 9 #291
• Disable customIdp test and example:
  The custom idp example and test do not work in keycloak 10, because the interfaces that our customIdp implements, have changed in the keycloak latest version.
  We need to make decide which keycloak version we going to support and test for the customIdp
• Fix for google-custom-idp not existing. this scenario was already covered by the above point so unneeded, the custom config is still checked

[hawknewton]

Ideally we'd support both and detect the server version at runtime.

[tomrutsaert]

If you are talking about customidp, yes i agree.
This is about starting the discussion en in mean time helping 10.0.1 version pass in #294.

If you are talking about #291 fix, this fix does support both and does not need runtime version check.