Pin links to user guide in javadoc to specific version

[JINU-CHANG]

Fixes #5273

What's Changed?

• Improved the handling of the hard-coded
  https://docs.junit.org/current link in Javadoc by making it conditional on the build environment.
• When building documentation locally, links to the User Guide in Javadoc now point to the
  locally built User Guide generated as part of the same build.
  This allows cross-references to documentation for unreleased features to be verified locally.
• In CI or release build environments, the existing behavior is preserved and links continue to
  point to https://docs.junit.org/current, ensuring that published documentation remains unchanged.

Below are the results showing that the links were correctly updated after building the project.

Before

After

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes

[mpkorstanje]

While you have grepped to confirm that a substitution happened, I don't think you have tested by actually clicking through the documentation. 😉

[JINU-CHANG]

@mpkorstanje

Thank you for the review!
With your feedback, I tested the links again by clicking through the documentation.
I also fixed the incorrect path, so when building locally, the links now successfully navigate to the locally build documentation.

1. The link has been replaced.

2. The link navigates to the locally build documentation.

[mpkorstanje]

Looks much better! But while that does up date the Javadoc for the different project modules. The actual javadoc for the website is generated and aggregated in the documentation module. You'll want to look at documentation.gradle.kts for details.

To test you'll have to run ./gradlew antora and open the url that is logged in the console.

[JINU-CHANG]

@mpkorstanje

I had missed that javadoc is generated in the documentation module 😅
I've moved the code to documentation.gradle.kts and confirmed the links are changed correctly by running ./gradlew antora. To distinguish between local and CI environments, I used System.getenv("CI") == "true".

Thank you for your helpful guidance!

[mpkorstanje]

Looks good now.

I had missed that javadoc is generated in the documentation module 😅

No worries. Your changes weren't bad. The documentation of each modules goes into its javadoc.jar for that module. And it wouldn't be a bad thing to pin that documentation too. Could you please restore the code that updated those modules and add it to the current changes.

You might be able to restore the code by finding the original commit in git reflog.

[testlens-app]

🔎 No tests executed 🔎

🏷️ Commit: d935857
▶️ Tests: 0 executed
⚪️ Checks: 0/0 completed

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[JINU-CHANG]

@mpkorstanje
I've restored the earlier changes and added them back to this PR !
Unlike in the documentation module, this code was written without considering the local environment, since the User Guide is built with Antora. Is this the right code change?