[ZEPPELIN-6541] Pin maven-checkstyle-plugin version so it is actually applied

[ParkGyeongTae]

What is this PR for?

The root pom.xml declares a plugin.checkstyle.version property (2.17) intended to pin the maven-checkstyle-plugin version used across all modules, but the plugin's <pluginManagement> declaration never referenced it via a <version> tag. As a result Maven silently resolved a different, non-deterministic plugin version regardless of what the property said — confirmed locally: the property said 2.17, but the build actually ran checkstyle:3.4.0:check. This PR adds the missing <version>${plugin.checkstyle.version}</version> tag and bumps the property to 3.6.0 (the current latest release) so the pinned version is the one that actually runs.

What type of PR is it?

Improvement

Todos

• Add <version>${plugin.checkstyle.version}</version> to the maven-checkstyle-plugin block in <pluginManagement>
• Bump plugin.checkstyle.version from 2.17 to 3.6.0

What is the Jira issue?

ZEPPELIN-6541

How should this be tested?

./mvnw -pl shell verify -DskipTests

Confirm the log shows checkstyle:3.6.0:check (not an arbitrary/older version) and the build completes with BUILD SUCCESS. No module overrides the plugin version locally, so all modules using maven-checkstyle-plugin inherit the pinned version consistently.

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need to update? No.
• Is there breaking changes for older versions? No — build-time only change, no runtime behavior affected.
• Does this needs documentation? No.

[tbonelee]

One thing worth weighing before wiring it back up: that <version> reference wasn't just never added, it was removed on purpose in #4884 ([ZEPPELIN-6138] Update Apache Parent), which un-pinned ~10 plugins at once to defer their versions to the parent pom. It just left the plugin.checkstyle.version property behind as leftover cruft.

So re-pinning would special-case checkstyle away from the parent-managed version, while the other plugins from that commit stay parent-managed. Unless there's a concrete reason to need 3.6.0, would just deleting the orphaned property fit the ticket's intent better? Curious what you think.

[ParkGyeongTae]

Good catch, thanks for digging into the #4884 history — you're right.

I re-checked: the <version> tag was removed intentionally in ZEPPELIN-6138 as part of deferring ~10 plugins to the Apache parent pom's managed versions, and plugin.checkstyle.version was just leftover cruft from that change, not a missing reference that needed to be restored.

I've updated this PR (and the Jira description) to remove the orphaned property instead of re-pinning it, so maven-checkstyle-plugin stays consistent with the other plugins from #4884 that are parent-managed. Verified locally that the build still runs checkstyle (now inherited from the parent pom, currently 3.4.0) and passes.

PTAL, thanks again for catching this.