Connect giftcards with customer accounts (#5126)

Connect giftcards with customer accounts, show giftcards during checkout and in account , show giftcard list in backend customer view

src/tests/presale/test_checkout.py

@@ -5488,3 +5488,22 @@ class CustomerCheckoutTestCase(BaseCheckoutTestCase, TestCase):
         with scopes_disabled():
             assert order.positions.first().used_membership == m_correct1
             assert order.positions.first().attendee_name == 'John Doe'
+
+    def test_giftcard_customer_offered(self):
+        with scopes_disabled():
+            gc = self.orga.issued_gift_cards.create(currency="EUR", customer=self.customer)
+            gc.transactions.create(value=23, acceptor=self.orga)
+            ugc = self.customer.usable_gift_cards()
+            assert len(ugc) == 1
+            CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=now() + timedelta(minutes=10)
+            )
+        self.client.post('/%s/%s/checkout/customer/' % (self.orga.slug, self.event.slug), {
+            'customer_mode': 'login',
+            'login-email': 'john@example.org',
+            'login-password': 'foo',
+        }, follow=True)
+        response = self.client.get('/%s/%s/checkout/payment/' % (self.orga.slug, self.event.slug), follow=True)
+        assert 'Gift card' in response.content.decode()
+        assert '(1 available)' in response.content.decode()