ci: automate GitHub Releases on version tags

Add a release job that triggers on v* tags, extracts the relevant
CHANGELOG section via awk, and creates a GitHub Release with gh cli.
Depends on unit and integration passing before publishing.

Author: mrmx

.github/workflows/ci.yml

@@ -3,6 +3,7 @@ name: CI
 on:
   push:
     branches: [main]
+    tags: ['v*']
   pull_request:
     branches: [main]
 
@@ -45,3 +46,27 @@ jobs:
             exit 0
           fi
           mvn -B -Dtest='*IntegrationTest' test
+
+  release:
+    needs: [unit, integration]
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/v')
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+      - name: Extract changelog for ${{ github.ref_name }}
+        id: changelog
+        run: |
+          VERSION="${GITHUB_REF_NAME#v}"
+          NOTES=$(awk "/^## \[$VERSION\]/{found=1; next} found && /^## \[/{exit} found{print}" CHANGELOG.md)
+          echo "notes<<EOF" >> "$GITHUB_OUTPUT"
+          echo "$NOTES" >> "$GITHUB_OUTPUT"
+          echo "EOF" >> "$GITHUB_OUTPUT"
+      - name: Create GitHub Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh release create "$GITHUB_REF_NAME" \
+            --title "$GITHUB_REF_NAME" \
+            --notes "${{ steps.changelog.outputs.notes }}"