Add typeahead suggestions for voucher tag field (#6058)

Suggest existing tags as the user types in the voucher tag field.
Waiting list voucher tags are excluded from suggestions.

src/tests/control/test_vouchers.py

@@ -44,7 +44,7 @@ from tests.base import SoupTestMixin, extract_form_fields
 
 from pretix.base.models import (
     Event, Item, ItemVariation, Order, OrderPosition, Organizer, Quota, Team,
-    User, Voucher,
+    User, Voucher, WaitingListEntry,
 )
 
 
@@ -771,3 +771,38 @@ class VoucherFormTest(SoupTestMixin, TransactionTestCase):
 
         assert len(doc.select('.alert-warning ul li')) == 1  # Check that there's exactly 1 item in the warning list
         assert doc.text.count('Order DEDUP') == 1  # Check that the order is listed exactly once
+
+    def test_tag_typeahead(self):
+        with scopes_disabled():
+            self.event.vouchers.create(item=self.ticket, code='AAAAAAA', tag='early-bird')
+            self.event.vouchers.create(item=self.ticket, code='BBBBBBB', tag='early-vip')
+            self.event.vouchers.create(item=self.ticket, code='CCCCCCC', tag='sponsor')
+
+        url = '/control/event/%s/%s/vouchers/tags/typeahead' % (self.orga.slug, self.event.slug)
+        resp = self.client.get(url + '?q=early')
+
+        assert resp.status_code == 200
+        data = json.loads(resp.content.decode())
+        names = [r['name'] for r in data['results']]
+
+        assert 'early-bird' in names
+        assert 'early-vip' in names
+        assert 'sponsor' not in names
+
+    def test_tag_typeahead_excludes_waiting_list(self):
+        with scopes_disabled():
+            v = self.event.vouchers.create(item=self.ticket, code='AAAAAAA', tag='waiting-list')
+            WaitingListEntry.objects.create(
+                event=self.event, item=self.ticket, email='foo@example.com', voucher=v
+            )
+            self.event.vouchers.create(item=self.ticket, code='BBBBBBB', tag='walk-ins')
+
+        url = '/control/event/%s/%s/vouchers/tags/typeahead' % (self.orga.slug, self.event.slug)
+        resp = self.client.get(url + '?q=wa')
+
+        assert resp.status_code == 200
+        data = json.loads(resp.content.decode())
+        names = [r['name'] for r in data['results']]
+
+        assert 'walk-ins' in names
+        assert 'waiting-list' not in names