Fix github.repository_owner not being upper-case

.github/workflows/dart.yml

@@ -31,10 +31,14 @@ jobs:
       - uses: docker/setup-buildx-action@v3
         with:
           buildkitd-flags: --debug
+      - id: lower-repo
+        name: Repository to lowercase
+        run: |
+          echo "repository=${GITHUB_REPOSITORY_OWNER@L}" >> $GITHUB_OUTPUT
       - uses: docker/login-action@v3
         with:
           registry: ghcr.io
-          username: ${{ github.repository_owner }}
+          username: ${{ steps.lower-repo.outputs.repository }}
           password: ${{ secrets.REGISTRY_TOKEN || secrets.GITHUB_TOKEN }}
       - uses: docker/build-push-action@v6
         with:
@@ -43,5 +47,5 @@ jobs:
           platforms: linux/amd64,linux/arm64
           push: true
           tags: |
-            ghcr.io/${{ github.repository_owner }}/yolks:dart_${{ matrix.tag }}
+            ghcr.io/${{ steps.lower-repo.outputs.repository }}/yolks:dart_${{ matrix.tag }}
             ${{ github.repository_owner == 'pelican-eggs' && format('ghcr.io/parkervcp/yolks:dart_{0}', matrix.tag) || '' }}