feat(gitpod): Install SDKMAN in GitHub runners and GitPod, and keep JDK versions up-to-date

[gounthar]

Background

In issues and discussions #119 and #120, we discussed the possibility of compiling plugins before and after applying recipes. The main challenge is installing and switching between various JDK versions during this process.

Solution

This PR implements the following features:

1. JDK Installation:

   • Adds Temurin JDKs from version 8 to 21 to the GitPod Workspace (defaulting to 17).
   • Creates scripts to install SDKMAN and Temurin JDKs 8-21 on any Linux machine.

2. Version Management:

   • Implements an updating mechanism using updatecli to keep JDK versions current.

3. Configuration:

   • Creates and maintains a property file (plugin-modernizer-cli/src/main/resources/sdkman.properties) listing JDK versions and their installation paths.

Potential Usage

The Maven Invoker Library might allow us to launch a new Maven clean environment while specifying the JDK version (possibly through JAVA_HOME).

Limitations

While this setup may not be sufficient to automatically switch between installed JDKs during recipe application, it should assist developers in manually switching when migrating plugins between JDK versions (e.g., from JDK 6 to 11, or 11 to 17).

Next Steps

1. Evaluate the effectiveness of this setup in practical plugin modernization scenarios.
2. Explore ways to integrate automatic JDK switching during the recipe application process.
3. Consider expanding support to non-Linux environments if needed.

Feedback and suggestions for improvement are welcome.

It's perfectly normal that the updatecli GitHub Action fails, as it tries to modify files that don't exist yet (plugin-modernizer-cli/src/main/resources/sdkman.properties) and parts of files that are not there yet (as the ARG in the Dockerfile). That issue will be solved when these changes will be part of the main branch.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jonesbusy]

Looks update cli failed. Excep that looks good on my side

[gounthar]

It is supposed to fail, as it is trying to update a file that doesn't exist yet.
Once merged, that should not happen anymore.