Index structure metadata in ES

arkindex/project/elastic.py

+from arkindex_common.enums import MetaType
 from collections.abc import Sequence
 from itertools import chain
 from django.conf import settings
@@ -94,6 +95,7 @@ class ESElement(Document):
     corpus = Keyword()
     # Used exclusively for sorting
     parents = Keyword()
+    structure = Keyword()
     transcriptions = Nested(ESTranscriptionInnerDoc)
     date_range = RawDateRange(format='yyyy||yyyy-MM||yyyy-MM-dd')
 
@@ -136,6 +138,10 @@ class ESElement(Document):
                 element.name
                 for element in Element.objects.get_ascending(instance.id)
             ],
+            structure=[
+                md.value
+                for md in instance.metadatas.filter(type=MetaType.Structure)
+            ],
             transcriptions=list(map(
                 ESTranscriptionInnerDoc.from_model,
                 transcriptions,