Add Groovy version for spring-boot-to-micronaut-at-configuration-at-bean-at-factory

[sdelamo]

The guide guides/spring-boot-to-micronaut-at-configuration-at-bean-at-factory is missing a Groovy version.

Expected work:

• Add the Groovy sample implementation for the guide.
• For multi-application guides, add the Groovy implementation under each application directory that needs it.
• Update guides/spring-boot-to-micronaut-at-configuration-at-bean-at-factory/metadata.json to include GROOVY in languages.
• Run ./gradlew springBootToMicronautAtConfigurationAtBeanAtFactoryBuild --stacktrace.
• Run ./gradlew springBootToMicronautAtConfigurationAtBeanAtFactoryRunTestScript --stacktrace.

This issue was created from an audit of guides missing Java, Groovy, or Kotlin variants. Groovy variants are intentionally not requested for Graal/GraalVM-specific guides.