Add GitHub Actions CI workflow for Maven build and test

[ntung]

Summary

JSBML currently has no automated CI pipeline. This issue proposes adding a GitHub Actions workflow to build and test the project on every push and pull request, generate test coverage reports via JaCoCo (see #316), and publish them to GitHub Pages.

Proposed workflow

Create .github/workflows/ci.yml:

name: CI

on:
  push:
    branches: [ main, master ]
  pull_request:
    branches: [ main, master ]

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        java-version: [ '8', '11', '17', '21' ]

    steps:
      - uses: actions/checkout@v4

      - name: Set up JDK ${{ matrix.java-version }}
        uses: actions/setup-java@v4
        with:
          java-version: ${{ matrix.java-version }}
          distribution: temurin
          cache: maven

      - name: Build and test
        run: mvn --batch-mode clean verify

  coverage:
    runs-on: ubuntu-latest
    needs: build
    if: github.event_name == 'push' && github.ref == 'refs/heads/master'
    permissions:
      pages: write
      id-token: write
    environment:
      name: github-pages
      url: ${{ steps.deploy.outputs.page_url }}

    steps:
      - uses: actions/checkout@v4

      - name: Set up JDK 11
        uses: actions/setup-java@v4
        with:
          java-version: '11'
          distribution: temurin
          cache: maven

      - name: Run all tests and generate aggregate coverage report
        run: mvn --batch-mode clean verify jacoco:report-aggregate

      - name: Upload Pages artifact
        uses: actions/upload-pages-artifact@v3
        with:
          path: target/site/jacoco-aggregate

      - name: Deploy to GitHub Pages
        id: deploy
        uses: actions/deploy-pages@v4

Rationale

build job

• Matrix across Java 8, 11, 17, and 21 LTS — the source/target are set to 1.7 so it compiles under all of them; this catches regressions across LTS versions.
• clean verify covers the full Maven lifecycle including integration tests.
• cache: maven caches ~/.m2 to keep run times short.

coverage job

• Runs only on pushes to master (not on every PR) to avoid unnecessary Page deployments.
• Uses JaCoCo's report-aggregate goal to produce a unified HTML report across all submodules (core, extensions, modules). This requires the JaCoCo changes proposed in Enable test coverage reporting via JaCoCo #316.
• Publishes the report to GitHub Pages using the native actions/upload-pages-artifact + actions/deploy-pages approach (no third-party action needed).
• The live coverage report URL is surfaced as the job's environment URL in the Actions UI.

One-time repository setup

Enable GitHub Pages in Settings → Pages → Source: GitHub Actions before the first workflow run.

Next steps

A PR adding this file can be submitted once maintainers agree on the approach. The JaCoCo pom.xml changes (issue #316) should land first or in the same PR so the coverage job has something to report.