Improve development-related documentation

[vy]

No description provided.

[ppkarwasz]

This is a long overdue change, thanks!

I believe we've only just started drafting our Contributing Guide. While we do have a Development section that explains how to set up a local development environment, we should also create a separate guide focused specifically on contributing. This new guide should outline the requirements for submitting a pull request or making other types of contributions. It would help experienced Java developers quickly understand the (often arbitrary) project-specific contribution rules without needing to wade through setup instructions.

We can include a shortened version of our Contributing Guide as the checklist in our pull request template—for example, we could use something like this:

Checklist

Before we can review and merge your changes, please go through the checklist below. If you're still working on some items, feel free to submit your pull request as a draft—our CI will help guide you through the remaining steps.

✅ Required checks

• License: I confirm that my changes are submitted under the Apache License, Version 2.0.

• Commit Signatures: All commits are signed and verifiable (see GitHub Docs on Commit Signature Verification).

• Code Formatting: The code is formatted according to the project’s style guide.

  How to check and fix formatting

  • To check formatting: ./mvnw spotless:check
  • To fix formatting: ./mvnw spotless:apply

• Build & Tests: I verified that the project builds and all unit tests pass.

  How to build the project

  Run: ./mvnw verify

🧪 Tests (select one)

• I have added or updated tests to cover my changes.
• No additional tests are needed for this change.

📝 Changelog (select one)

• I added a changelog entry in src/changelog/.2.x.x (see Changelog Entry File Guide).
• This is a trivial change and does not require a changelog entry.

[vy]

@ppkarwasz, applied your suggestions in 0ee4732.