title: Implement a REST API in a Grails app
body: <p>I was wondering what would be the best approach to make a Grails app offer a <em>RESTful API</em> (some CRUD actions mainly) that can be used by a web service, e.g. when you want to build a corresponding <em>iOS</em> app to your browser-based app or anything else. </p>
  
  <p>I thought of building a separate part in my Grails application that takes calls from <code>www.mywebapp.com/api/someAction</code> so that I can reuse the Service layer. How would I do the URL mapping then? Only having one big <code>ApiController</code> does not sound very groovy.</p>
  
  <p>Or is there any better approach I did not know of? This approach <strong>must</strong> support something like <em>OAuth</em> to authenticate the user who is calling the Web service.</p>