Merge pull request #5504 from overleaf/jpa-old-cdn-probe

[web] add a probe for the old/current CDN

GitOrigin-RevId: 59e34e793edceebb49a8d6fa4e3e6716b921d09d

services/web/frontend/js/cdn-load-test.js

@@ -6,4 +6,10 @@ if (window.ExposedSettings.isOverleaf) {
     captureMessage('CDN test image load error (cdn.overleaf.net)')
   })
   cdnLoadTest.src = 'https://cdn.overleaf.net/img/1p.gif'
+
+  const cdnLoadTestOld = document.createElement('img')
+  cdnLoadTestOld.addEventListener('error', function () {
+    captureMessage('CDN test image load error (cdn.overleaf.com)')
+  })
+  cdnLoadTestOld.src = 'https://cdn.overleaf.com/img/1p.gif'
 }