Do not populate left pane on initial link

ts/util/postLinkExperience.ts

@@ -0,0 +1,32 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { onTimeout } from '../services/timers';
+
+class PostLinkExperience {
+  private hasNotFinishedSync: boolean;
+
+  constructor() {
+    this.hasNotFinishedSync = false;
+  }
+
+  start() {
+    this.hasNotFinishedSync = true;
+
+    // timeout "post link" after 10 minutes in case the syncs don't complete
+    // in time or are never called.
+    onTimeout(Date.now() + 60 * 60 * 10 * 1000, () => {
+      this.stop();
+    });
+  }
+
+  stop() {
+    this.hasNotFinishedSync = false;
+  }
+
+  isActive(): boolean {
+    return this.hasNotFinishedSync === true;
+  }
+}
+
+export const postLinkExperience = new PostLinkExperience();