Use entire queryset for offer report download rather than paginated one (#4105)

* Use entire queryset for offer report download rather than paginated queryset

* Add offer order report test

* Specify order number in create_order factory

src/oscar/apps/dashboard/offers/views.py

     def render_to_response(self, context):
         if self.request.GET.get('format') == 'csv':
             formatter = OrderDiscountCSVFormatter()
-            return formatter.generate_response(context['order_discounts'],
+            return formatter.generate_response(self.get_queryset(),
                                                offer=self.offer)
         return super().render_to_response(context)

tests/functional/dashboard/test_offer.py

 from django.utils import timezone
 
 from oscar.apps.offer import models
+from oscar.apps.order.models import OrderDiscount
 from oscar.test import factories, testcases
 
 
 
         self.assertNotIn(offer_a, offer_b.combinations.all())
 
+    def test_create_offer_order_report(self):
+        order1 = factories.create_order(number="100001")
+        order2 = factories.create_order(number="100002")
+        offer = factories.create_offer()
+        OrderDiscount.objects.create(order=order1, offer_id=offer.id)
+        OrderDiscount.objects.create(order=order2, offer_id=offer.id)
+
+        report_url = "%s%s" % (reverse("dashboard:offer-detail", kwargs={'pk': offer.pk}), "?format=csv")
+        response = self.get(report_url)
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.headers["Content-Type"], "text/csv")
+        self.assertIn("100001", response.content.decode("utf-8"))
+        self.assertIn("100002", response.content.decode("utf-8"))
+
 
 class TestOfferListSearch(testcases.WebTestCase):
     is_staff = True