title: Is Telegram username unique?
body: <p>When I work over bot development, I found that messages that comes from user have some field called <code>username</code>, e. g.</p>
  
  <pre><code>{
      update_id: 123567890,
      message: {
          message_id: 1,
          from: {
              id: 1234567890,
              is_bot: false,
              first_name: "Kappa",
              last_name: "Pride",
              username: "kappapride",
          }
      ...
  }
  </code></pre>
  
  <p>Does this field contains an unique value, such as <code>id</code> field? I know, I can make a TG link with it (like <code>@kappapride</code>), but I'm not sure if this field presents for each TG user.</p>