code: @RequestMapping(method = RequestMethod.POST, value = "/workflowInstance/{woinRefNum}/signal/{signal}",
              produces = {MediaType.APPLICATION_JSON_VALUE, MediaType.TEXT_XML_VALUE})
      public ResponseEntity<Void> sendSignal( @PathVariable long woinRefNum, @PathVariable String signal, @RequestBody String argument ){
          facade.sendSignalToWorkflowInstance( woinRefNum, signal, JsonUtil.deserialize( argument ) );
          return new ResponseEntity<>( HttpStatus.NO_CONTENT );
      }
docs: Notifies all waiting signal work items of the given workflow instance and the given signal name.
  
  Technically, sets the work item's result value and updates the status to EXECUTED.
  
  <pre>
  Request:  POST /workflowInstance/1/signal/invoice {argument: {refNum:3, invoiceAmount: "10 Euro"}}
  Response: NO_CONTENT
  </pre>