Migrate cp-kafka-rest to UBI9 micro base image

[Krish Vora (KrishVora01)]

Summary

• Switch from single-stage cp-base-java to 3-stage multi-stage build using cp-base-java-micro
• Stage 1: Extract package_dedupe tool from cp-base-java-micro
• Stage 2: Install confluent-kafka-rest, confluent-telemetry, confluent-security RPMs into /microdir using dnf --installroot
• Stage 3: Selectively COPY to cp-base-java-micro final image
• Remove unused confluent-security subdirs (schema-registry, connect, ksql)
• User migration: appuser hardcoded -> ${APP_UID}/${APP_GID} variables
• Add UBI9_VERSION build arg to pom.xml for both spotify and fabric8 plugins

Test plan

• CI build passes (Maven + Docker)
• Image starts and REST endpoint is reachable on port 8082
• Container runs as non-root user
• CFK e2e-plaintext-kraft test passes with overridden cp-kafka-rest image
• Kind local test script: ./run-kind-e2e-kafka-rest.sh

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Migrates the cp-kafka-rest image build to a UBI9-based multi-stage approach to reduce final image size by installing RPMs into an installroot and selectively copying artifacts into a cp-base-java-micro final image.

Changes:

• Convert kafka-rest/Dockerfile.ubi9 from single-stage cp-base-java to a 3-stage build (tools → builder → final) using cp-base-java-micro.
• Install confluent-kafka-rest, confluent-telemetry, and confluent-security into /microdir, remove unused security subdirs, and dedupe jars before copying into the final image.
• Pass UBI9_VERSION as a Docker build arg via both spotify and fabric8 Maven Docker plugins.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
kafka-rest/pom.xml	Adds UBI9_VERSION build-arg wiring for spotify + fabric8 Docker build plugins.
kafka-rest/Dockerfile.ubi9	Implements multi-stage UBI9 builder installroot flow and switches final image to cp-base-java-micro with selective copies and UID/GID-based ownership.

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[Copilot]

UBI9_VERSION is used in the FROM registry.access.redhat.com/ubi9:${UBI9_VERSION} instruction but the ARG UBI9_VERSION has no default. If the build arg isn’t provided (e.g., local docker build), the build will fail due to an invalid base image reference. Consider providing a safe default (or switching to a pinned default) and/or documenting/enforcing the required build arg in the build tooling.

[Copilot]

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