/// create Vec<PageRequest> from (total: u64, page_size: u64)
    pub fn make_page_requests(total: u64, page_size: u64) -> Vec<PageRequest> {
        let mut result = vec![];
        let pages = PageRequest::new(1, page_size).set_total(total).pages();
        for idx in 0..pages {
            let current_page = PageRequest::new(idx + 1, page_size).set_total(total);
            result.push(current_page);
        }
        result
    }