Implementing API Pagination

@GetMapping("/orders")
public PageResponse<OrderResponse> list(
    @RequestParam(defaultValue="0") int page,
    @RequestParam(defaultValue="20") int size) {
    var pg = PageRequest.of(page, size, Sort.by("placedAt").descending());
    return mapper.toResponse(orderRepo.findAll(pg));
}

-- cursor encodes (placed_at, id) of last item
SELECT * FROM orders
WHERE (placed_at, id) < (?, ?)
ORDER BY placed_at DESC, id DESC
LIMIT 21;  -- 1 extra to detect hasNext

{ "items": [], "page": 0, "size": 20, "totalElements": 0,
  "totalPages": 0, "hasNext": false, "hasPrev": false }

"_links": {
  "self":  { "href": "/orders?page=2&size=20" },
  "first": { "href": "/orders?page=0&size=20" },
  "prev":  { "href": "/orders?page=1&size=20" },
  "next":  { "href": "/orders?page=3&size=20" },
  "last":  { "href": "/orders?page=99&size=20" }
}