automatically close openapi PRs with no changes (#33532)

.github/workflows/openapi-decorate.yml

@@ -53,6 +53,21 @@ jobs:
       - name: Decorate the dereferenced OpenAPI schemas
         run: script/rest/update-files.js --decorate-only
 
+      - name: Check if pull request should be closed
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_URL: ${{ github.event.pull_request.html_url }}
+        run: |
+          echo "If there are no changes, exit"
+          NUM_FILES_CHANGED=$(git diff --name-only -- lib/rest/static/decorated | wc -l)
+          if [[ $NUM_FILES_CHANGED -eq 0 ]]
+            then
+              echo "No decorated file changes found"
+              gh pr comment "$PR_URL" --body "🤖 This pull request has no changes to lib/rest/static/decorated, so it is being closed automatically."
+              gh pr close "$PR_URL"
+              exit 0
+          fi
+
       - name: Check in the decorated files
         uses: EndBug/add-and-commit@050a66787244b10a4874a2a5f682130263edc192
         with: