pkg-build: bundle metadata.json inside debs.tar.gz for S3 upload

.github/workflows/pkg-build-reusable-workflow.yml

@@ -615,6 +615,29 @@ jobs:
           mkdir -p build-area
           tar -C build-area -xzf docker-build-area.tgz
 
+      - name: Generate metadata.json
+        env:
+          SRCPKG_NAME: ${{ needs.test.outputs.srcpkg_name }}
+          SRCPKG_VERSION: ${{ needs.test.outputs.srcpkg_version }}
+          SUITE: ${{ needs.resolve.outputs.suite }}
+        run: |
+          set -euxo pipefail
+          python3 - build-area/metadata.json <<'PY'
+          import json
+          import os
+          import sys
+
+          data = {
+              "source-package": os.environ["SRCPKG_NAME"],
+              "version": os.environ["SRCPKG_VERSION"],
+              "suite": os.environ["SUITE"],
+          }
+
+          with open(sys.argv[1], "w") as f:
+              json.dump(data, f, indent=2)
+              f.write("\n")
+          PY
+
       - name: Stage debs for S3 proposed upload
         run: |
           set -euxo pipefail
@@ -623,7 +646,7 @@ jobs:
           if [ "${#debs[@]}" -eq 0 ]; then
             echo "No .deb files found in build-area; skipping debs.tar.gz creation"
           else
-            tar -czf s3-proposed/debs.tar.gz -C build-area "${debs[@]}"
+            tar -czf s3-proposed/debs.tar.gz -C build-area "${debs[@]}" metadata.json
           fi
 
       - name: Upload proposed debs to S3