ENH: Validate and upload artifact from build

Validates the qemu image then creates artifacts from the Github Actions
including the SHA256 (which OpenStack can use as part of the image
upload) as artifacts that stay around for ~1 week

.github/workflows/amphora_builder.yaml

@@ -24,5 +24,29 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+
       - name: Exec Amphora build
-        run: cd amphora-image-builder && ./build.sh
+        run: |
+          cd $GITHUB_WORKSPACE/amphora-image-builder
+          ./build.sh
+          sudo chown -R $USER:$USER $GITHUB_WORKSPACE/output
+      
+      - name: Check image is valid
+        run: |
+          cd $GITHUB_WORKSPACE 
+          sudo apt-get update && sudo apt-get install -y --no-install-recommends qemu-utils
+          qemu-img check output/amphora-x64-$(date +%Y-%m-%d)-haproxy.qcow2
+
+      - name: SHA256 image
+        run: |
+          cd $GITHUB_WORKSPACE 
+          sha256sum output/amphora-x64-$(date +%Y-%m-%d)-haproxy.qcow2 > output/amphora-x64-$(date +%Y-%m-%d)-haproxy.qcow2.sha256
+      
+      - name: Upload image
+        uses: actions/upload-artifact@v4
+        with:
+          name: amphora-image
+          if-no-files-found: error
+          path: output/*qcow2*
+          compression-level: 0  # qcow2 files are already compressed
+          retention-days: 7