title: Grails file upload not using correct content-type
body: <p>I created a file upload in Grails, but I can't find a way to get the request to use <code>Content-Type:multipart/form-data</code>. The requests are being sent with
  <code>Content-Type:application/x-www-form-urlencoded</code>.</p>
  
  <p>This is my form</p>
  
  <pre><code>        &lt;g:uploadForm controller='asset' action='upload'&gt;
              &lt;label&gt;Select file(s) to upload&lt;/label&gt;
              &lt;input type='file' id='fileUpload' name='filesToUpload' multiple /&gt;
              &lt;g:submitButton name="upload" value="Upload"/&gt;
          &lt;/g:uploadForm&gt;
  </code></pre>
  
  <p>In Config.groovy, <code>grails.mime.types</code> contains <code>multipartForm: 'multipart/form-data'</code> and <code>grails.web.disable.multipart=false</code>. I am using Spring Security, and the <code>AssetsController</code> is <code>@Secured</code>.</p>
  
  <p>How do I get the requests to be sent with <code>Content-Type:multipart/form-data</code>?</p>