ci: add GitHub Actions workflow

Add GitHub Actions CI workflow that runs the full test suite via
`mvn clean verify` and builds the standalone distribution on every
push to master and on pull requests.

Author: yeikel

.github/workflows/ci.yml

@@ -0,0 +1,69 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        es-version:
+          - "8.19.15"
+          - "9.0.8"
+          - "9.1.10"
+          - "9.2.8"
+          - "9.3.4"
+          - "9.4.1"
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Java 8
+        uses: actions/setup-java@v4
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+          cache: 'maven'
+
+      - name: Run tests (ES ${{ matrix.es-version }})
+        run: mvn clean verify
+        env:
+          ELASTICSEARCH_VERSION: ${{ matrix.es-version }}
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Java 8
+        uses: actions/setup-java@v4
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+          cache: 'maven'
+
+      - name: Build standalone distribution
+        run: mvn clean install -Pstandalone -DskipTests
+
+      - name: Upload standalone artifacts
+        uses: actions/upload-artifact@v7.0.1
+        if: always()
+        with:
+          name: standalone-jar
+          path: target/kafka-connect-elasticsearch-15.2.0-SNAPSHOT-standalone.jar
+          retention-days: 90
+
+      - name: Build distribution
+        run: mvn clean install -DskipTests
+
+      - name: Upload distribution artifact
+        uses: actions/upload-artifact@v7.0.1
+        if: always()
+        with:
+          name: distribution-package
+          path: target/kafka-connect-elasticsearch-15.2.0-SNAPSHOT-package
+          retention-days: 90