Add integration tests for jkube.java.version base image selection

[ash-thakur-rh]

Context

eclipse-jkube/jkube#3916 adds a jkube.java.version shared property that lets users explicitly select a JDK-specific base image (jkube-java-11/-17/-21/-25). The implementation PR is eclipse-jkube/jkube#3931.

Unit tests are included in the main repo. This issue tracks the integration tests called for in the acceptance criteria.

What to test

Verify that jkube.java.version is honored in generated manifests for at least Spring Boot and Quarkus, for both Maven and Gradle.

Test cases

1. Maven + Spring Boot — set <jkube.java.version>21</jkube.java.version> in pom.xml properties, run k8s:resource, verify the generated Deployment uses jkube-java-21 as the base image.
2. Maven + Quarkus — same as above with a Quarkus project.
3. Gradle + Spring Boot — set jkube.java.version=21 in gradle.properties, run k8sResource, verify the generated Deployment uses jkube-java-21.
4. Gradle + Quarkus — same as above with a Quarkus project.
5. Unset — verify default jkube-java (latest) is used when the property is not set.

Blocked on

• eclipse-jkube/jkube#3931 being merged.

[manusa]

I'd rather see the tests being implemented first and failing, then disabled on main. And then, how the production code actually fix those.

[ash-thakur-rh]

PR: #413

Adds integration tests for jkube.java.version base image selection covering Spring Boot and Quarkus for both Maven and Gradle. Tests follow the full k8s:build → k8s:resource → k8s:apply → k8s:undeploy lifecycle and verify JDK 21 via java -version on the deployed pod. Tests are @Disabled on main per guidance — to be enabled once eclipse-jkube/jkube#3931 is ready.