testing - export to tar

Author: Zeitsperre

.github/workflows/docker-testing.yml

@@ -48,7 +48,7 @@ jobs:
           platforms: linux/amd64
           provenance: mode=max
           sbom: true
-          outputs: type=cacheonly
+          outputs: type=oci,dest=./image.tar
           push: false
       - name: Run Docker image
         uses: addnab/docker-run-action@4f65fabd2431ebc8d299f8e5a018d79a769ae185 # v3.0.0