✨(documents) add content field as an S3 object

The content field is a writable property on the model which is persisted
in object storage. We take advantage of the versioning, robustness and
scalability of S3.

src/backend/core/api/fields.py

@@ -0,0 +1,24 @@
+"""A JSONField for DRF to handle serialization/deserialization."""
+import json
+
+from rest_framework import serializers
+
+
+class JSONField(serializers.Field):
+    """
+    A custom field for handling JSON data.
+    """
+
+    def to_representation(self, value):
+        """
+        Convert the JSON string to a Python dictionary for serialization.
+        """
+        return value
+
+    def to_internal_value(self, data):
+        """
+        Convert the Python dictionary to a JSON string for deserialization.
+        """
+        if data is None:
+            return None
+        return json.dumps(data)