Implement single logout

Author: albertoperdomo

index.js

@@ -140,11 +140,16 @@ app.get("/analytics", restrict, function (req, res) {
 });
 
 app.get("/logout", function (req, res) {
-    // destroy the user's session to log them out
-    // will be re-created next request
-    req.session.destroy(function () {
-        res.redirect("/");
-    });
+  const mbLogoutUrl = new URL("/auth/logout", METABASE_SITE_URL);
+  
+  // destroy the user's session to log them out
+  // will be re-created next request
+  req.session.destroy(function () {
+    // sign user out of Metabase by loading /auth/logout in a hidden iframe
+    res.send(`
+      You have been logged out. <a href="/login">Log in</a>
+      <iframe src="${mbLogoutUrl}" hidden></iframe>`);
+  });
 });
 
 app.get("/login", function (req, res) {