title: Purpose of Content-Type undefined in AngularJS FileUpload
body: <p>For uploading files from angular to a Spring MVC REST WebService, people seem to be setting Content-Type : undefined header in the AJAX request.</p>
  
  <p>What is the purpose of this type of content-type and is it required by Spring MultiPart?</p>
  
  <pre><code>$http.post(uploadUrl, fd, {
    transformRequest : angular.identity,
    headers : {
     'Content-Type' : undefined
    }
  //...
  }
  </code></pre>