Migrate minimum JDK version from 8 to 17

[Copilot]

Updates minimum required Java version from JDK 8 to JDK 17 across build configuration, CI workflows, and documentation.

Changes

• pom.xml: Updated compiler source/target to 17, enforcer plugin requirement to 17
• GitHub Actions:
  • Removed JDK 8/11 from CI matrix, now tests against 17 and 21
  • Updated quality checks and CodeQL analysis to use JDK 17
  • Moved coverage artifact generation from JDK 8 to JDK 17
• README.md: Updated compatibility badges and statements to reflect JDK 17+ requirement

This is a breaking change. Users on JDK 8-16 must upgrade to JDK 17 or later.

Original prompt

Objective

Migrate the htmlunit-neko project from JDK 8 to JDK 17 as the minimum required Java version.

Changes Required

1. Update pom.xml

• Change maven.compiler.source from 8 to 17 (line 23)
• Change maven.compiler.target from 8 to 17 (line 24)
• Update the requireJavaVersion in maven-enforcer-plugin from 1.8.0 to 17 (line 265)

2. Update GitHub Actions Workflows

.github/workflows/ci.yml

• Update the Java version matrix to reflect JDK 17 as the minimum
• Current matrix: ['8', '11', '17', '21'] (line 16)
• New matrix should be: ['17', '21'] or ['17', '21', '23'] depending on testing strategy
• Update the "quality" job to use Java 17 instead of Java 8 (line 64)

.github/workflows/codeql-analysis.yml

• Change the Java version setup from '8' to '17' (line 37)

3. Update README.md

• Update the compatibility statement from "Java 8+ Compatible" to "Java 17+ Compatible" (around line 23)
• Review any other references to Java 8 compatibility and update them to Java 17

Notes

• Ensure backward compatibility is not broken for users
• The project currently tests against Java 8, 11, 17, and 21 in CI
• After migration, minimum supported version will be Java 17
• This is a breaking change and should be documented in release notes
• Consider updating version number to reflect the major change (e.g., 5.0.0)

Testing

• Ensure all tests pass with JDK 17 as the minimum version
• Verify CI builds successfully on all target Java versions
• Run quality checks (Checkstyle, SpotBugs, PMD) with JDK 17

This pull request was created from Copilot chat.

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