Compare lowercase structural metadata

arkindex/documents/api/search.py

@@ -56,7 +56,7 @@ class ElementSearch(SearchAPIView):
         if structural_metadata:
             search = search.filter(
                 'wildcard',
-                structural_metadata='*{}*'.format(structural_metadata)
+                structural_metadata='*{}*'.format(structural_metadata.lower())
             )
 
         if element_type:

arkindex/project/elastic.py

@@ -139,7 +139,7 @@ class ESElement(Document):
                 for element in Element.objects.get_ascending(instance.id)
             ],
             structural_metadata=[
-                md.value
+                md.value.lower()
                 for md in instance.metadatas.filter(type=MetaType.Structural)
             ],
             transcriptions=list(map(