title: Handling of batch requests in SAPUI5 with sap.ui.model.odata.v2.ODataModel
body: <p>If I change a property of an OData entity to an invalid value (SAPUI5 client) and send that value to SAP Gateway Server using <code>submitChanges</code> I got the following message in the log file:</p>
  
  <blockquote>
    <p>Service returned messages for entities that were not requested. This
    might lead to wrong message processing and loss of messages</p>
  </blockquote>
  
  <p>Now I would expect that the callback for "error" would be called but it is always "success".</p>
  
  <p>Inside the callback for success I have a list of responses (in this case with an error).</p>
  
  <p>Now I am asking me, why the error callback is not called?</p>
  
  <p>I assume because the overall batch response is most of the time "OK" also if one request of the batch contains an error?</p>
  
  <p>So do I have to implement error handling in the success callback? Or should the server send an overall error response?</p>
  
  <p>I am using SAPUI5 1.28.15 (with 1.30.6 at least the cited message seems to be removed) and switched batch mode to "on" (if batch mode is off, callback will not be called!).</p>