Remove document flat_tags helper, update document index template accordingly

apps/dynamic_search/templates/search/indexes/documents/document_text.txt

@@ -11,5 +11,9 @@
 {{ object.file_mimetype }}
 {{ object.description|default:' ' }}
 {{ object.flat_comments }}
-{{ object.flat_tags }}
+
+{% for tag in object.tags.all %}
+    {{ tag }}
+{% endfor %}
+
 {{ object.uuid }}

apps/tags/__init__.py

@@ -66,11 +66,4 @@ class_permissions(Tag, [
     PERMISSION_TAG_VIEW,
 ])
 
-
-def flat_tags(document):
-    return u' '.join(document.tags.values_list('name', flat=True))
-
-
 Document.add_to_class('tags', TaggableManager())
-Document.add_to_class('flat_tags', flat_tags)
-