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 +24,22 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+
       - name: Exec Amphora build
         run: cd amphora-image-builder && ./build.sh
+
+      - name: Check image is valid
+        run: cd $GITHUB_WORKSPACE && qemu-img check output/amphora-x64-$(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
+          path: |
+            $GITHUB_WORKSPACE/output/amphora-x64-$(date +%Y-%m-%d)-haproxy.qcow2
+            $GITHUB_WORKSPACE/output/amphora-x64-$(date +%Y-%m-%d)-haproxy.qcow2.sha256
+
+          retention-days: 7