title: How do I set default host for url helpers in rails?
body: <p>I would like to do something like this</p>
  
  <pre><code>config.default_host = 'www.subdomain.example.com'
  </code></pre>
  
  <p>in some of my configuration files, so that <code>object_url</code> helpers (<code>ActionView::Helpers::UrlHelper</code>) produce links beginning with <a href="http://www.subdomain.example.com" rel="noreferrer">http://www.subdomain.example.com</a></p>
  
  <p>I have tried to search the docs but I did not find anything except <code>ActionMailer</code> docs and <a href="http://api.rubyonrails.org/classes/Rails/Configuration.html" rel="noreferrer">http://api.rubyonrails.org/classes/Rails/Configuration.html</a> which is not useful for me, because I do not know in which pat to look. Is there a place which describes the whole structure of Rails::Initializer.config?</p>