docs: def admin_page_ordering(request):
      """
      Updates the ordering of pages via AJAX from within the admin.
      """
  
      def get_id(s):
          s = s.split("_")[-1]
          return int(s) if s.isdigit() else None
      page = get_object_or_404(Page, id=get_id(request.POST['id']))
      old_parent_id = page.parent_id
      new_parent_id = get_id(request.POST['parent_id'])
      new_parent = Page.objects.get(id=new_parent_id) if new_parent_id else None
  
      try:
          page.get_content_model().can_move(request, new_parent)
      except PageMoveException as e:
          messages.error(request, e)
          return HttpResponse('error')
  
      # Perform the page move
      if new_parent_id != page.parent_id:
          # Parent changed - set the new parent and re-order the
          # previous siblings.
          page.set_parent(new_parent)
          pages = Page.objects.filter(parent_id=old_parent_id)
          for i, page in enumerate(pages.order_by('_order')):
              Page.objects.filter(id=page.id).update(_order=i)
      # Set the new order for the moved page and its current siblings.
      for i, page_id in enumerate(request.POST.getlist('siblings[]')):
          Page.objects.filter(id=get_id(page_id)).update(_order=i)
  
      return HttpResponse("ok")