HSEARCH-3661 Use aggregations key more consistently

e.g. instead of `aggs` in bucket aggregations

Author: marko-bekhta

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/aggregation/impl/AbstractElasticsearchBucketAggregation.java

@@ -23,14 +23,16 @@
 public abstract class AbstractElasticsearchBucketAggregation<K, V>
 		extends AbstractElasticsearchNestableAggregation<Map<K, V>> {
 
+	protected static final JsonAccessor<JsonObject> REQUEST_AGGREGATIONS_ACCESSOR =
+			JsonAccessor.root().property( "aggregations" ).asObject();
+
 	private static final JsonAccessor<JsonObject> REQUEST_REVERSE_NESTED_ACCESSOR =
 			JsonAccessor.root().property( "reverse_nested" ).asObject();
 
 	private static final String ROOT_DOC_COUNT_NAME = "root_doc_count";
 	private static final JsonAccessor<JsonObject> REQUEST_AGGREGATIONS_ROOT_DOC_COUNT_ACCESSOR =
 			JsonAccessor.root().property( "aggregations" ).property( ROOT_DOC_COUNT_NAME ).asObject();
 
-	protected static final String INNER_EXTRACTOR_KEY = "innerExtractorKey";
 	protected static final String INNER_EXTRACTOR = "innerExtractor";
 
 	AbstractElasticsearchBucketAggregation(AbstractBuilder<K, V> builder) {

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/aggregation/impl/ElasticsearchRangeAggregation.java

@@ -66,7 +66,7 @@ protected void doRequest(JsonObject outerObject, JsonObject innerObject, Aggrega
 				aggregation.request( context, AggregationKey.of( "agg" ), subOuterObject ) );
 
 		if ( !subOuterObject.isEmpty() ) {
-			outerObject.add( "aggs", subOuterObject );
+			REQUEST_AGGREGATIONS_ACCESSOR.set( outerObject, subOuterObject );
 		}
 	}
 

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/aggregation/impl/ElasticsearchTermsAggregation.java

@@ -72,7 +72,7 @@ protected void doRequest(JsonObject outerObject, JsonObject innerObject, Aggrega
 				aggregation.request( context, AggregationKey.of( "agg" ), subOuterObject ) );
 
 		if ( !subOuterObject.isEmpty() ) {
-			outerObject.add( "aggs", subOuterObject );
+			REQUEST_AGGREGATIONS_ACCESSOR.set( outerObject, subOuterObject );
 		}
 	}