Fix and improve configuration validation when using the `strict` profile

Issue

Running with the strict profile fails, for example in the local env with cargo. This is due to some new, valid properties were introduced but are not reflected in the UaaConfiguration class, which is out of date. To verify, run:

./gradlew '-Dspring.profiles.active=strict' run

The app will fail to start. Check uaa/build/reports/tests/uaa-server.log:

[...]
Unable to find property 'external_groups' on class: org.cloudfoundry.identity.uaa.impl.config.UaaConfiguration$Scim
 in 'string', line 20, column 20:
      external_groups: ['organizations.acme|cn=test_org ...
[...]

Next steps

• gh-3262 partially addresses this, to ensure . It makes sure the validation logic does not trip up when running UAA with cargo/uaa.yml. However, that PR does not look at the business logic of validating properties.
• We should ensure that we have proper validation of the configuration.
• When migrating to Java config and the Boot 3+, we should Spring Boot's facilities for validating configuration: use @ConfigurationProperties object and do our validation there, removing the need for a dedicated YamlConfigurationValidator.

Start by reviewing the UaaConfiguration class and the dedicated YamlConfigurationValidator, then run ./gradlew '-Dspring.profiles.active=strict' run and inspect uaa/build/reports/tests/uaa-server.log. Compare the strict profile properties with the configuration model and existing validation behavior. Done means valid properties no longer prevent startup and configuration validation remains properly enforced.