Post install CI cypress user

For: https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/1086

Supercedes: https://repo1.dso.mil/platform-one/big-bang/pipeline-templates/pipeline-templates/-/merge_requests/155

Using the new baby-yoda-ci.json realm config, we now have a config where MFA + email verification is disabled, as well as having any registered user automatically assigned to IL2. This MR adds a post install hook that will leverage Keycloak's REST API and create a Cypress user for E2E testing.