fix: use administrativeMetadata for ListSets request

oaipmh-core/src/main/java/info/textgrid/middleware/SetListDeliverer.java

@@ -94,13 +94,13 @@ public class SetListDeliverer {
           "doc['administrativeMetadata.dcterms:identifier'].value + '" + DH_FIELD_DIVIDER
               + "' + doc['descriptiveMetadata.dc:title'].value");
 
-      // Do filter all collections (via descriptiveMetadata.dc:format) AND get out all the child
-      // objects and collections (NO descriptiveMetadata.dc:relation), so we get exactly one set per
-      // root collection only!
+      // Do filter all collections (via administrativeMetadata.dcterms:format) AND get out all the
+      // child, objects and collections (NO administrativeMetadata.dc:relation), so we get exactly
+      // one set per root collection only!
       AggregationBuilder collectionFilter = AggregationBuilders.filter(DH_COLLECTION_FILTER_NAME,
           QueryBuilders.boolQuery()
-              .mustNot(QueryBuilders.existsQuery("descriptiveMetadata.dc:relation"))
-              .must(QueryBuilders.matchPhraseQuery("descriptiveMetadata.dc:format",
+              .mustNot(QueryBuilders.existsQuery("administrativeMetadata.dcterms:relation"))
+              .must(QueryBuilders.matchPhraseQuery("administrativeMetadata.dcterms:format",
                   TextGridMimetypes.DARIAH_COLLECTION)));
       AggregationBuilder collectionFilterTerm = AggregationBuilders
           .terms(DH_COLLECTION_FILTER_TERM_NAME).script(mergeCollectionIDAndTitle).size(DH_SIZE);