Usernames: Fetch own username from /whoami not /profile

ts/textsecure/SendMessage.ts

@@ -2236,4 +2236,7 @@ export default class MessageSender {
   async deleteUsername(): Promise<ReturnType<WebAPIType['deleteUsername']>> {
     return this.server.deleteUsername();
   }
+  async whoami(): Promise<ReturnType<WebAPIType['whoami']>> {
+    return this.server.whoami();
+  }
 }