refactor: Move export into separate app

export/serializers/__init__.py

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+from . import (
+    people
+)

export/serializers/base.py

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+"""
+Serialize models to and deserialize from JSON.
+"""
+
+from collections import OrderedDict
+import typing
+
+from rest_framework import serializers
+
+
+class FlattenedModelSerializer(serializers.ModelSerializer):
+    @classmethod
+    def flatten_data(cls, data,
+                     sub_type: typing.Type = dict,
+                     sub_value_accessor: typing.Callable = lambda x: x.items()) -> typing.OrderedDict:
+        """
+        Flatten a dictionary so that subdictionaries become a series of `key[.subkey[.subsubkey ...]]` entries
+        in the top level dictionary.
+
+        Works for other data structures (e.g. DRF Serializers) by providing suitable values for the
+        `sub_type` and `sub_value_accessor` parameters.
+
+        :param data: Dictionary or other data structure to flatten
+        :param sub_type: Type to recursively flatten
+        :param sub_value_accessor: Function to access keys and values contained within sub_type.
+        """
+        data_out = OrderedDict()
+
+        for key, value in sub_value_accessor(data):
+            if isinstance(value, sub_type):
+                # Recursively flatten nested structures of type `sub_type`
+                sub_flattened = cls.flatten_data(value,
+                                                 sub_type=sub_type,
+                                                 sub_value_accessor=sub_value_accessor).items()
+
+                # Enter recursively flattened values into result dictionary
+                for sub_key, sub_value in sub_flattened:
+                    # Keys in result dictionary are of format `key[.subkey[.subsubkey ...]]`
+                    data_out[f'{key}.{sub_key}'] = sub_value
+
+            else:
+                data_out[key] = value
+
+        return data_out
+
+    @property
+    def column_headers(self) -> typing.List[str]:
+        """
+        Get all column headers that will be output by this serializer.
+        """
+        fields = self.flatten_data(self.fields,
+                                   sub_type=serializers.BaseSerializer,
+                                   sub_value_accessor=lambda x: x.fields.items())
+
+        return list(fields)
+
+    def to_representation(self, instance) -> typing.OrderedDict:
+        """
+
+        """
+        rep = super().to_representation(instance)
+
+        rep = self.flatten_data(rep)
+
+        return rep

export/serializers/people.py

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+import typing
+
+from rest_framework import serializers
+
+from people import models
+
+from . import base
+
+
+class PersonSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = models.Person
+        fields = [
+            'pk',
+            'name',
+        ]
+
+
+class PersonExportSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = models.Person
+        fields = [
+            'pk',
+            'name',
+            'core_member',
+            'gender',
+            'age_group',
+            'nationality',
+            'country_of_residence',
+        ]
+
+
+class RelationshipSerializer(base.FlattenedModelSerializer):
+    source = PersonSerializer()
+    target = PersonSerializer()
+
+    class Meta:
+        model = models.Relationship
+        fields = [
+            'pk',
+            'source',
+            'target',
+        ]
+
+    @property
+    def column_headers(self) -> typing.List[str]:
+        headers = super().column_headers
+
+        # Add relationship questions to columns
+        for question in models.RelationshipQuestion.objects.all():
+            headers.append(question.slug)
+
+        return headers
+
+    def to_representation(self, instance):
+        rep = super().to_representation(instance)
+
+        try:
+            # Add relationship question answers to data
+            for answer in instance.current_answers.question_answers.all():
+                rep[answer.question.slug] = answer.slug
+
+        except AttributeError:
+            pass
+
+        return rep