Verify backstage plugin for keycloak works with Keycloak 22

[nickboldt]

What needs to be done?

With the end of RH SSO 7.x announced as June 30, 2025, and the release of Keycloak 22, we need to verify that the keycloak plugin in Backstage / Janus Showcase / RHDH work with the latest.

https://github.com/janus-idp/backstage-plugins/tree/main/plugins/keycloak-backend

This is a testing/engineering task.

Refs:

• https://access.redhat.com/support/policy/updates/jboss_notes/#p_sso
• https://www.keycloak.org/2023/07/keycloak-2200-released.html and https://www.keycloak.org/2023/10/keycloak-2205-released (22.0.5 is latest, as of Oct 24, 2023)

However we can't do anything until Backstage supports ESM:

• backend: full support for ESM packages backstage/backstage#12218
• Reminder: Upgrade keycloak client once Backstage supports ESM backstage-plugins#47

[davidfestal]

This would also impact the Dynamic backend plugin loading feature as well, which is NodeRequire-based, and has never been tested / validated with ESM modules (direct import or transitive deps).