[#56] Update repeating subfields indexing logic

The previous field names based on indexes didn't allow to retrieve
results easily. We are now flattening all values for the same subfield
to at least get a text hit.

See #281 (comment)

ckanext/dcat/plugins/__init__.py

@@ -147,16 +147,18 @@ def before_dataset_index(self, dataset_dict):
             pass
 
         if schema:
-            # TODO: https://github.com/ckan/ckanext-dcat/pull/281#discussion_r1610549936
             for field in schema['dataset_fields']:
                 if field['field_name'] in dataset_dict and 'repeating_subfields' in field:
-                    for index, item in enumerate(dataset_dict[field['field_name']]):
+                    for item in dataset_dict[field['field_name']]:
                         for key in item:
-                            value = dataset_dict[field['field_name']][index][key]
+                            value = item[key]
                             if not isinstance(value, dict):
                                 # Index a flattened version
-                                new_key = f'{field["field_name"]}_{index}_{key}'
-                                dataset_dict[new_key] = value
+                                new_key = f'{field["field_name"]}__{key}'
+                                if not dataset_dict.get(new_key):
+                                    dataset_dict[new_key] = ""
+                                dataset_dict[new_key] += " " + value
+
                     dataset_dict.pop(field['field_name'], None)
 
         return dataset_dict