Usernames: Fetch own username from /whoami not /profile

ts/util/updateOurUsername.ts

@@ -0,0 +1,16 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export async function updateOurUsername(): Promise<void> {
+  if (!window.textsecure.messaging) {
+    throw new Error(
+      'updateOurUsername: window.textsecure.messaging not available'
+    );
+  }
+
+  const me = window.ConversationController.getOurConversationOrThrow();
+  const { username } = await window.textsecure.messaging.whoami();
+
+  me.set({ username });
+  window.Signal.Data.updateConversation(me.attributes);
+}