Migrate Java 5 - 17 code to Java 21

[sebr72]

Stop using old Java code where possible.
Remove calls to deprecated methods in tests

[Copilot]

Pull Request Overview

This PR modernizes the Java codebase by migrating from deprecated Java APIs to modern alternatives, specifically:

• Replacing deprecated String.repeat() implementations with loop-based string appending
• Switching from deprecated URL constructors to URL.of() with URI parameters
• Updating to modern StatusPrinter2 class instead of deprecated StatusPrinter
• Migrating from new HashMap<String, String>() to diamond operator new HashMap<>()
• Replacing list.get(0) and list.get(list.size()-1) with getFirst() and getLast() methods

Reviewed Changes

Copilot reviewed 136 out of 136 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
PrintApiTest.java	Replaced manual loop with String.repeat() for test data generation
ExamplesTest.java	Updated imports, exception handling, and URL construction methods
Multiple test files	Migrated HashMap instantiation to use diamond operator throughout
Various layer/processor test files	Updated list access methods to use getFirst()/getLast()
Core source files	Applied modern Java patterns including switch expressions and instanceof pattern matching

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