ISSUE #631: lowercase the image repository name in github actions (#919)

Author: RomanFilip

.github/workflows/build-notebooks-TEMPLATE.yaml

@@ -42,6 +42,12 @@ jobs:
 
     steps:
 
+      # image repository name must be lowercase
+      - name: downcase IMAGE_REGISTRY and CACHE
+        run: |
+          echo "IMAGE_REGISTRY=${IMAGE_REGISTRY,,}" >>${GITHUB_ENV}
+          echo "CACHE=${CACHE,,}" >>${GITHUB_ENV}
+
       - uses: actions/checkout@v4
 
       - run: mkdir -p $TMPDIR