title: What is the corresponding artifact for Config.groovy of grails 2.x in grails 3.x?
body: <p>I want to migrate an application from grails 2.4.4 to grails 3.3.9.
  As the structure of the conf directory in grails 2.x is completely different from 3.x, there is no config.groovy in 3.x anymore. In config.groovy of 2.x I used to define lists of constants for my select boxes like:</p>
  
  <pre><code>  metals=['au','ag','pl']    
  </code></pre>
  
  <p>and I accessed them via </p>
  
  <pre><code>static List getMetals() {
      grails.util.Holders.config.metals
  }    
  </code></pre>
  
  <p>in my groovy code.</p>
  
  <p>What is the corresponding way in 3.x?</p>