Add a simple test mode (#1181)

- [x] Provide data model and configuration toggle
- [x] Allow to delete individual test orders
- [x] Add tests
- [x] Add a prominent warning message to the backend if test mode orders exist (even though test mode is off), as this leads to wrong statistics
- [x] Decide if and how to generate invoices for test orders as invoice numbers cannot be repeated or should not have gaps.
- [x] Decide if and how we expose test orders through the API, since our difference pull mechanism relies on the fact that orders cannot be deleted.
- [x] Decide if and how we want to couple test modes of payment providers?
- [ ] pretix.eu: Ignore test orders for billing
- [ ] Adjust payment providers: Mollie, bitpay, cash, fakepayment, sepadebit

![download](https://user-images.githubusercontent.com/64280/53009081-fe420d80-343a-11e9-8361-b8511c988598.png)

src/tests/api/test_orders.py

@@ -181,6 +181,7 @@ TEST_REFUNDS_RES = [
 TEST_ORDER_RES = {
     "code": "FOO",
     "status": "n",
+    "testmode": False,
     "secret": "k24fiuwvu8kxz3y1",
     "email": "dummy@dummy.test",
     "locale": "en",
@@ -242,6 +243,11 @@ def test_order_list(token_client, organizer, event, order, item, taxrule, questi
     resp = token_client.get('/api/v1/organizers/{}/events/{}/orders/?code=BAR'.format(organizer.slug, event.slug))
     assert [] == resp.data['results']
 
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/orders/?testmode=false'.format(organizer.slug, event.slug))
+    assert [res] == resp.data['results']
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/orders/?testmode=true'.format(organizer.slug, event.slug))
+    assert [] == resp.data['results']
+
     resp = token_client.get('/api/v1/organizers/{}/events/{}/orders/?status=n'.format(organizer.slug, event.slug))
     assert [res] == resp.data['results']
     resp = token_client.get('/api/v1/organizers/{}/events/{}/orders/?status=p'.format(organizer.slug, event.slug))
@@ -1352,6 +1358,7 @@ def test_order_create(token_client, organizer, event, item, quota, question):
     assert o.total == Decimal('23.25')
     assert o.status == Order.STATUS_PENDING
     assert o.sales_channel == "web"
+    assert not o.testmode
 
     p = o.payments.first()
     assert p.provider == "banktransfer"
@@ -1423,6 +1430,22 @@ def test_order_create_sales_channel_invalid(token_client, organizer, event, item
     assert resp.data == {'sales_channel': ['Unknown sales channel.']}
 
 
+@pytest.mark.django_db
+def test_order_create_in_test_mode(token_client, organizer, event, item, quota, question):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    res['testmode'] = True
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    o = Order.objects.get(code=resp.data['code'])
+    assert o.testmode
+
+
 @pytest.mark.django_db
 def test_order_create_attendee_name_optional(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
@@ -2502,3 +2525,26 @@ def test_refund_create_invalid_payment(token_client, organizer, event, order):
         ), format='json', data=res
     )
     assert resp.status_code == 400
+
+
+@pytest.mark.django_db
+def test_order_delete(token_client, organizer, event, order):
+    resp = token_client.delete(
+        '/api/v1/organizers/{}/events/{}/orders/{}/'.format(
+            organizer.slug, event.slug, order.code
+        )
+    )
+    assert resp.status_code == 403
+
+
+@pytest.mark.django_db
+def test_order_delete_test_mode(token_client, organizer, event, order):
+    order.testmode = True
+    order.save()
+    resp = token_client.delete(
+        '/api/v1/organizers/{}/events/{}/orders/{}/'.format(
+            organizer.slug, event.slug, order.code
+        )
+    )
+    assert resp.status_code == 204
+    assert not Order.objects.filter(code=order.code).exists()