Story

As a user of RHDH, I want to documentation on how to create a custom Keycloak transformer so that control the user/group mappings in RHDH

Users would need to know how to create their own backend module that utilizes the `keycloakTransformerExtensionPoint` to provide custom user/group transformers to the keycloak backend to custom how users/groups are mapped into entities in RHDH.

Refer to documentation in the plugin README on setting up the module: https://github.com/janus-idp/backstage-plugins/tree/main/plugins/keycloak-backend#new-backend-configuration 

The README also contains details on expected fields/paramaters to pass into the transformers.

Background

See https://issues.redhat.com/browse/RHIDP-2643

Dependencies and Blockers

QE impacted work

Documentation impacted work

Acceptance Criteria

upstream documentation updates (design docs, release notes etc)

Technical enablement / Demo