Add a checksum to the container image

Author: heerener

.github/workflows/release.yaml

@@ -32,7 +32,8 @@ jobs:
         working-directory: ${{runner.workspace}}/hpc-resource-provisioner
       - name: Build and push container
         run: |
-          docker build -t hpc-resource-provisioner:${REL_TAG}
+          SOURCE_CHECKSUM=$(find hpc_provisioner -type f -exec sha256sum {} \; | sha256sum | awk '{print $1}')
+          docker build --label "org.opencontainers.image.checksum=${SOURCE_CHECKSUM}" --label-t hpc-resource-provisioner:${REL_TAG}
           docker login -u bbpbuildbot -p ${BBPBUILDBOT_DOCKERHUB_PASSWORD}
           docker push hpc-resource-provisioner:${REL_TAG} docker.io/bluebrain/hpc-resource-provisioner:${REL_TAG}
           docker push hpc-resource-provisioner:${REL_TAG} docker.io/bluebrain/hpc-resource-provisioner:latest