docs: function verifyUsernameDoesNotExist(req, res, next) {
    var username = req.body.username;
    var dataStore = req.app.dataStore;
  
    // Check for an existing employee REST resource - /employees/{username}
    var resource = new swagger.Resource('/employees', username, null);
    dataStore.get(resource, function(err, resource) {
      if (resource) {
        // The username already exists, so send an HTTP 409 (Conflict)
        res.sendStatus(409);
      }
      else {
        next();
      }
    });
  }