title: REST API - using PUT method for removing attributes
body: <p>We are restrained on using only PUT method for updating a resource, so PATCH is not an option (unfortunately).</p>
  
  <p>Context: there are cases of fields mapped on attributes which are defined as Optional and Editable, meaning the user may remove the previous inputted and previously saved value.</p>
  
  <p>My question:  which is the best option to save this change via the PUT method? (removing the attribute from the resource)</p>
  
  <p>AFAIK there are 3 options available:</p>
  
  <ul>
  <li><p>a) send the attribute with an empty value, eg. <code>"invoiceSerial": ""</code></p></li>
  <li><p>b) send the attribute with a clear null, eg. <code>"invoiceSerial": null</code></p></li>
  <li><p>c) don`t send the attribute at all, and on the server side it should process all missing editable&amp;optional attributes by removing them from the stored object</p></li>
  </ul>
  
  <p>i can`t find any best practice out there, so any hint to some standard documentation is appreciated.</p>