Handle null seat details for segment passengers

The API documentation for `Order.slices.segments.passengers.seat` said
that the value wasn't nullable, which wasn't correct. These changes
update the `Order` model to allow that field to be returned with a null
value.

https://duffel.com/docs/api/orders/schema#orders-schema-slices-slices-segments-slices-segments-passengers-slices-segments-passengers-seat

Author: Sasha Gerrand

duffel_api/models/order.py

@@ -125,7 +125,8 @@ def __init__(self, json):
             if key == "baggages":
                 value = [OrderSliceSegmentPassengerBaggage(v) for v in value]
             elif key == "seat":
-                value = OrderSliceSegmentPassengerSeat(value)
+                if value is not None:
+                    value = OrderSliceSegmentPassengerSeat(value)
             elif key == "cabin_class":
                 if value not in OrderSliceSegmentPassenger.allowed_cabin_classes:
                     raise OrderSliceSegmentPassenger.InvalidCabinClass(value)

tests/fixtures/get-orders.json

@@ -236,14 +236,7 @@
                   "cabin_class": "economy",
                   "cabin_class_marketing_name": "Economy Basic",
                   "passenger_id": "passenger_0",
-                  "seat": {
-                    "designator": "14B",
-                    "disclosures": [
-                      "Do not seat children in exit row seats",
-                      "Do not seat passengers with special needs in exit row seats"
-                    ],
-                    "name": "Exit row seat"
-                  }
+                  "seat": null
                 }
               ]
             }

tests/test_orders.py

@@ -11,12 +11,30 @@ def test_get_order_by_id(requests_mock):
     with fixture("get-order-by-id", url, requests_mock.get, 200) as client:
         order = client.orders.get("id")
         assert order.id == "ord_00009hthhsUZ8W4LxQgkjo"
+        assert not order.live_mode
+        assert len(order.passengers) == 1
         assert order.synced_at == datetime.datetime(2020, 4, 11, 15, 48, 11)
         assert len(order.slices) == 1
-        assert len(order.passengers) == 1
-        assert not order.live_mode
         slice = order.slices[0]
         assert slice.origin_type == "airport"
+        assert len(order.slices[0].segments) == 1
+        assert len(order.slices[0].segments[0].passengers) == 1
+        passenger = order.slices[0].segments[0].passengers[0]
+        assert len(passenger.baggages) == 1
+        assert passenger.baggages[0].quantity == 1
+        assert passenger.baggages[0].type == "checked"
+        assert passenger.cabin_class == "economy"
+        assert passenger.cabin_class_marketing_name == "Economy Basic"
+        assert passenger.passenger_id == "passenger_0"
+        assert passenger.seat is not None
+        assert passenger.seat.designator == "14B"
+        assert len(passenger.seat.disclosures) == 2
+        assert passenger.seat.disclosures[0] == "Do not seat children in exit row seats"
+        assert (
+            passenger.seat.disclosures[1]
+            == "Do not seat passengers with special needs in exit row seats"
+        )
+        assert passenger.seat.name == "Exit row seat"
 
 
 def test_get_orders(requests_mock):
@@ -37,6 +55,17 @@ def test_get_orders(requests_mock):
         assert len(orders) == 1
         order = orders[0]
         assert order.id == "ord_00009hthhsUZ8W4LxQgkjo"
+        assert len(order.slices) == 1
+        assert len(order.slices[0].segments) == 1
+        assert len(order.slices[0].segments[0].passengers) == 1
+        passenger = order.slices[0].segments[0].passengers[0]
+        assert len(passenger.baggages) == 1
+        assert passenger.baggages[0].quantity == 1
+        assert passenger.baggages[0].type == "checked"
+        assert passenger.cabin_class == "economy"
+        assert passenger.cabin_class_marketing_name == "Economy Basic"
+        assert passenger.passenger_id == "passenger_0"
+        assert passenger.seat is None
         assert order.synced_at == datetime.datetime(2020, 4, 11, 15, 48, 11)