add add_to_reusable_medium to order-serializer

doc/api/resources/orders.rst

@@ -1070,6 +1070,7 @@ Creating orders
       * ``valid_until`` (optional, if both ``valid_from`` and ``valid_until`` are **missing** (not ``null``) the availability will be computed from the given product)
       * ``requested_valid_from`` (optional, can be set **instead** of ``valid_from`` and ``valid_until`` to signal a user choice for the start time that may or may not be respected)
       * ``use_reusable_medium`` (optional, causes the new ticket to take over the given reusable medium, identified by its ID)
+      * ``add_to_reusable_medium`` (optional, causes the new ticket to be added to the given reusable medium, identified by its ID)
       * ``discount`` (optional, only possible if ``price`` is set; attention: if this is set to not-``null`` on any position, automatic calculation of discounts will not run)
       * ``answers``
 

src/pretix/api/serializers/order.py

@@ -1043,13 +1043,15 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
     requested_valid_from = serializers.DateTimeField(required=False, allow_null=True)
     use_reusable_medium = serializers.PrimaryKeyRelatedField(queryset=ReusableMedium.objects.none(),
                                                              required=False, allow_null=True)
+    add_to_reusable_medium = serializers.PrimaryKeyRelatedField(queryset=ReusableMedium.objects.none(),
+                                                             required=False, allow_null=True)
 
     class Meta:
         model = OrderPosition
         fields = ('positionid', 'item', 'variation', 'price', 'attendee_name', 'attendee_name_parts', 'attendee_email',
                   'company', 'street', 'zipcode', 'city', 'country', 'state', 'is_bundled',
                   'secret', 'addon_to', 'subevent', 'answers', 'seat', 'voucher', 'valid_from', 'valid_until',
-                  'requested_valid_from', 'use_reusable_medium', 'discount')
+                  'requested_valid_from', 'use_reusable_medium', 'add_to_reusable_medium', 'discount')
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -1061,6 +1063,8 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
         with scopes_disabled():
             if 'use_reusable_medium' in self.fields:
                 self.fields['use_reusable_medium'].queryset = ReusableMedium.objects.all()
+            if 'add_to_reusable_medium' in self.fields:
+                self.fields['add_to_reusable_medium'].queryset = ReusableMedium.objects.all()
 
     def validate_secret(self, secret):
         if secret and OrderPosition.all.filter(order__event=self.context['event'], secret=secret).exists():
@@ -1076,6 +1080,9 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
             )
         return m
 
+    def validate_add_to_reusable_medium(self, m):
+        return self.validate_use_reusable_medium(m)
+
     def validate_item(self, item):
         if item.event != self.context['event']:
             raise ValidationError(
@@ -1149,6 +1156,13 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
             raise ValidationError(
                 {'discount': ['You can only specify a discount if you do the price computation, but price is not set.']}
             )
+
+        if data.get('use_reusable_medium') and data.get('add_to_reusable_medium'):
+            raise ValidationError({
+                'use_reusable_medium': ['You can only specify either use_reusable_medium or add_to_reusable_medium.'],
+                'add_to_reusable_medium': ['You can only specify either use_reusable_medium or add_to_reusable_medium.'],
+            })
+
         return data
 
 
@@ -1588,7 +1602,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 pos_data['attendee_name_parts'] = {
                     '_legacy': attendee_name
                 }
-            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k != 'answers' and k != '_quotas' and k != 'use_reusable_medium'})
+            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k not in ('answers', '_quotas', 'use_reusable_medium', 'add_to_reusable_medium')})
             if simulate:
                 pos.order = order._wrapped
             else:
@@ -1662,6 +1676,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         for pos_data in positions_data:
             answers_data = pos_data.pop('answers', [])
             use_reusable_medium = pos_data.pop('use_reusable_medium', None)
+            add_to_reusable_medium = pos_data.pop('add_to_reusable_medium', None)
             pos = pos_data['__instance']
             pos._calculate_tax(invoice_address=ia)
 
@@ -1703,8 +1718,17 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                         answ.options.add(*options)
 
                 if use_reusable_medium:
-                    use_reusable_medium.linked_orderpositions.add(pos)
+                    use_reusable_medium.linked_orderpositions.set([pos])
                     use_reusable_medium.log_action(
+                        'pretix.reusable_medium.linked_orderposition.changed',
+                        data={
+                            'by_order': order.code,
+                            'linked_orderposition': pos.pk,
+                        }
+                    )
+                if add_to_reusable_medium:
+                    add_to_reusable_medium.linked_orderpositions.add(pos)
+                    add_to_reusable_medium.log_action(
                         'pretix.reusable_medium.linked_orderposition.added',
                         data={
                             'by_order': order.code,