Generalize import process from orders to more models (#4002)

* Generalize import process from orders to more models

* Add voucher import

* Model import: Guess assignments of based on column headers

* Fix lock_seats being pointless

* Update docs

* Update doc/development/api/import.rst

Co-authored-by: Richard Schreiber <schreiber@rami.io>

* Update src/pretix/base/modelimport_vouchers.py

Co-authored-by: Richard Schreiber <schreiber@rami.io>

---------

Co-authored-by: Richard Schreiber <schreiber@rami.io>

src/tests/control/test_modelimport.py

@@ -35,14 +35,15 @@ def env():
         date_from=now(), plugins='pretix.plugins.banktransfer,pretix.plugins.paypal'
     )
     user = User.objects.create_user('dummy@dummy.dummy', 'dummy')
-    t = Team.objects.create(organizer=event.organizer, can_view_orders=True, can_change_orders=True)
+    t = Team.objects.create(organizer=event.organizer, can_view_orders=True, can_change_orders=True,
+                            can_change_vouchers=True)
     t.members.add(user)
     t.limit_events.add(event)
     return event, user
 
 
 @pytest.mark.django_db
-def test_import_csv_file(client, env):
+def test_orders_import_csv_file(client, env):
     client.login(email='dummy@dummy.dummy', password='dummy')
     r = client.get('/control/event/dummy/dummy/orders/import/')
     assert r.status_code == 200
@@ -65,3 +66,22 @@ Anke,Müller,anke@example.net
     assert b"Dieter" in r.content
     assert b"daniel@example.org" in r.content
     assert b"Anke" not in r.content
+
+
+@pytest.mark.django_db
+def test_vouchers_import_csv_file(client, env):
+    client.login(email='dummy@dummy.dummy', password='dummy')
+    r = client.get('/control/event/dummy/dummy/vouchers/import/')
+    assert r.status_code == 200
+
+    file = SimpleUploadedFile('file.csv', """Code,Product
+ABC123,Ticket
+
+""".encode("utf-8"), content_type="text/csv")
+
+    r = client.post('/control/event/dummy/dummy/vouchers/import/', {
+        'file': file
+    }, follow=True)
+    doc = BeautifulSoup(r.content, "lxml")
+    assert doc.select("select[name=code]")
+    assert b"ABC123" in r.content