upgrade-flakes: use github app

.github/workflows/upgrade-flakes.yml

@@ -18,6 +18,11 @@ jobs:
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+      - uses: actions/create-github-app-token@v1
+        id: app-token
+        with:
+          app-id: ${{ vars.CI_APP_ID }}
+          private-key: ${{ secrets.CI_APP_PRIVATE_KEY }}
       - name: Update flakes
         run: |
            nix flake update
@@ -27,3 +32,8 @@ jobs:
            nix run .#update-dev-private-narHash
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@v7
+        with:
+          title: Update flakes
+          token: ${{ steps.app-token.outputs.token }}
+          labels: |
+            auto-merge