Do not login or push to dockerhub if secrets not available in job

Author: ponyisi

.github/workflows/ci_servicex.yaml

@@ -105,14 +105,15 @@ jobs:
         uses: docker/setup-buildx-action@v3.10.0
       - name: Login to Docker Hub
         uses: docker/login-action@v3.3.0
+        if: ${{ github.secret_source == 'Actions' }}
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
       - name: Build and push
         uses: docker/build-push-action@v6.15.0
         with:
           context: ${{ matrix.app.dir_name }}
-          push: true
+          push: ${{ github.secret_source == 'Actions' }}
           tags: ${{ steps.extract_tag_name.outputs.imagetag }}
           cache-from: type=${{ format('registry,ref={0}',steps.extract_cache_name.outputs.cachetag) }}
           cache-to: type=${{ format('registry,ref={0}',steps.extract_cache_name.outputs.cachetag) }},mode=max