More /projects cache tuning

src/api.js

@@ -143,9 +143,15 @@ const getProjectMeta = async (projectId) => {
     // api.scratch.mit.edu has Cache-Control: max-age=240 and the tokens have a timestamp
     // that 300 seconds into the future. However that timestamp is consistently wrong,
     // so we shouldn't wait for it to be close to expiry.
-    return unixTimestamp - SECOND * 180;
+    return unixTimestamp - SECOND * 120;
   }, () => {
-    return apiQueue.queuePromise(`https://api.scratch.mit.edu/projects/${projectId}/?`);
+    // Send along a slightly random query string so we're more likely to get an uncached token if
+    // we just evicted an old cache entry.
+    // We're not going to send a traditional cachebuster like ?nocache=${Date.now()} because they've
+    // throttled those really bad in the past.
+    const ENDINGS = ['', '?', '/', '/?'];
+    const ending = ENDINGS[Math.floor(Math.random() * ENDINGS.length)];
+    return apiQueue.queuePromise(`https://api.scratch.mit.edu/projects/${projectId}${ending}`);
   });
 };