Refs #314 -- Read-only REST API (#513)

* initial commit

* API auth

* Hierarchical URLs

* Add session auth

* Strong hierarchy

* Add filters

* Add i18n fields, questions

* More viewsets and serializers

* Ticket download

* Add OrderPosition serializer

* View-level permissions

* More tests

* More tests

* Add basic API docs

* Add REST API to docs frontpage

* Tests for order endpoints

* Add invoice tests

* Voucher and waitinglist tests

* Doc draft

* order docs

* Docs on all viewsets

* Disable DRF docs, style sphinx, style browsable API

* Fix tests

* deprecated imports

* Test foo

* Attendee names

* Fix migration problems

* Remove browsable API, plugin integration

* Doc fixes

src/pretix/api/serializers/i18n.py

@@ -0,0 +1,31 @@
+from django.conf import settings
+from i18nfield.fields import I18nCharField, I18nTextField
+from rest_framework.fields import Field
+from rest_framework.serializers import ModelSerializer
+
+
+class I18nField(Field):
+    def __init__(self, **kwargs):
+        self.allow_blank = kwargs.pop('allow_blank', False)
+        self.trim_whitespace = kwargs.pop('trim_whitespace', True)
+        self.max_length = kwargs.pop('max_length', None)
+        self.min_length = kwargs.pop('min_length', None)
+        super().__init__(**kwargs)
+
+    def to_representation(self, value):
+        if value is None or value.data is None:
+            return None
+        if isinstance(value.data, dict):
+            return value.data
+        else:
+            return {
+                settings.LANGUAGE_CODE: str(value.data)
+            }
+
+
+class I18nAwareModelSerializer(ModelSerializer):
+    pass
+
+
+I18nAwareModelSerializer.serializer_field_mapping[I18nCharField] = I18nField
+I18nAwareModelSerializer.serializer_field_mapping[I18nTextField] = I18nField