public void OnAuthorization(HttpActionContext actionContext)
        {
            // allowing super/system admin queries anything
            if (_authorizationService.CanAccessEverything())
            {
                return;
            }

            // default to current user
            // note: only AgencyAdministrator is allowed so call CanWriteUser
            var currentUserId = _owinContext.GetCurrentUserId();
            var userId        = actionContext.GetOrSetQueryString("userId", currentUserId);

            if (!_authorizationService.CanWriteUser(userId))
            {
                actionContext.SetUnauthorizedResponse();
            }

            // note: only AgencyAdministrator is allowed so call CanWriteBuyerAccount
            var buyerAccountUuid = actionContext.GetQueryString <Guid?>("buyerAccountUuid");

            if (buyerAccountUuid.HasValue && !_authorizationService.CanWriteBuyerAccount(buyerAccountUuid.Value))
            {
                actionContext.SetUnauthorizedResponse();
            }
        }