title: How do you populate the host for image_url helper in a mailer?
body: <p>I have the asset host specified in my Rails 5.2.0 config:</p>
  
  <p><code>config.action_controller.asset_host = "assets.example.com"</code></p>
  
  <p>But the <code>image_url</code> helper still only returns the path without the host. I am using <code>&lt;%= image_url('/something') %&gt;</code> in my mailer view file. Whenever it renders it just uses the path <code>"/images/something"</code>.</p>