title: How to Convert Swift JSON / Dict Key camel to underscore without Codable?
body: <p>I want convert:</p>
  <pre><code>{
    &quot;userNickname&quot;: &quot;whatever&quot;,
    &quot;userId&quot;: &quot;123&quot;,
    &quot;date&quot;: &quot;2021-03-25T16:10:00Z&quot;
  }
  </code></pre>
  <p>to</p>
  <pre><code>{
    &quot;user_nick_name&quot;: &quot;whatever&quot;,
    &quot;user_id&quot;: &quot;123&quot;,
    &quot;date&quot;: &quot;2021-03-25T16:10:00Z&quot;
  }
  </code></pre>
  <p>But all the methods found so far are based on the codable protocol, or bugs generated during the conversion process, do you have any good suggestions?</p>