Implement middleware into newer lambdas

api/content-links.js

@@ -29,6 +29,19 @@ const handler = async (url) => {
   const internalLinks = [...internalLinksMap.entries()].sort((a, b) => b[1] - a[1]).map(entry => entry[0]);
   const externalLinks = [...externalLinksMap.entries()].sort((a, b) => b[1] - a[1]).map(entry => entry[0]);
 
+  // If there were no links, then mark as skipped and show reasons
+  if (internalLinks.length === 0 && externalLinks.length === 0) {
+    return {
+      statusCode: 400,
+      body: JSON.stringify({
+        skipped: 'No internal or external links found. '
+          + 'This may be due to the website being dynamically rendered, using a client-side framework (like React), and without SSR enabled. '
+          + 'That would mean that the static HTML returned from the HTTP request doesn\'t contain any meaningful content for Web-Check to analyze. '
+          + 'You can rectify this by using a headless browser to render the page instead.',
+        }),
+    };
+  }
+
   return { internal: internalLinks, external: externalLinks };
 };