Update the OIDC tests to use the 19.0.1 version of quay.io/keycloak/keycloak

The tests for OpenID Connect make use of the Keycloak container image. Currently, the tests are relying on the latest version. We should update this to use a fixed version of Keycloak instead, version 19.0.1.

Here's some additional context about this issue:

I was getting test failures regarding the container starting up successfully, when I looked closer I saw the only image I had in docker for keycloak was 5 months old so although the test is configured to use the latest - after deleting the image the test runs and has downloaded an image 4 weeks old.

We should use a specific version of Keycloak instead. As latest evolves our prior tags will no longer be buildable with tests if we just use latest.