public static <T> RestResponse<T> ok() {
        return new RestResponse<>();
    }
@Test
    public void testOk() {
        Assert.assertTrue(RestResponse.ok().isSuccess());
        Assert.assertEquals("Hello", RestResponse.ok("Hello").getPayload());

        RestResponse ok = RestResponse.ok("Hello", 200);
        Assert.assertEquals("Hello", ok.getPayload());
        Assert.assertTrue(ok.isSuccess());
    }