✨(backend) add a breadcrumb in the search response

In the search response, we want to display a breadcrumb for every
document returned. For this we added a "parents" property containing a list
documents, all are the parents of the current document (ordered by their
depth). With this we can easily create a breadcrumb.

src/backend/core/api/serializers.py

@@ -167,6 +167,17 @@ class ListDocumentSerializer(serializers.ModelSerializer):
         return instance.ancestors_deleted_at
 
 
+class SearchDocumentSerializer(ListDocumentSerializer):
+    """Serialize items for search."""
+
+    parents = ListDocumentSerializer(many=True, read_only=True)
+
+    class Meta:
+        model = models.Document
+        fields = ListDocumentSerializer.Meta.fields + ["parents"]
+        read_only_fields = ListDocumentSerializer.Meta.read_only_fields + ["parents"]
+
+
 class DocumentLightSerializer(serializers.ModelSerializer):
     """Minial document serializer for nesting in document accesses."""