Allow a client to query the status of an asynchronous request without returning the result if the request completed.

Add to 11.6 Asynchronous Requests : Once the asynchronous processing has completed, a GET request to the status monitor resource returns a 200 OK, or 204 No Content if the request included a Prefer header with a value of return=minimal . For OData 4.01 and greater responses, or OData 4.0 requests that include an Accept header that does not specify application/http, the response MUST include the AsyncResult response header. A response with 204 No Content MUST include a Location header that can be used to request the result of the completed asynchronous operation. The Location header may or may not contain the same values as returned by the previous request. In a response with 200 OK any other headers, along with the response body, represent the result of the completed asynchronous operation. If the GET request to the status monitor includes an OData-MaxVersion header with a value of 4.0 and no Accept header, or an Accept header that includes application/http, then the body of the final 200 OK response MUST be represented as an HTTP message, as described in [RFC7230] , which is the full HTTP response to the completed asynchronous operation.