Implement WithFieldName interface in ValuesSourceAggregationBuilder

Signed-off-by: David Zane <davizane@amazon.com>

Author: dzane17

server/src/main/java/org/opensearch/search/aggregations/support/ValuesSourceAggregationBuilder.java

@@ -40,6 +40,7 @@
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.core.xcontent.XContentParser;
 import org.opensearch.index.query.QueryShardContext;
+import org.opensearch.index.query.WithFieldName;
 import org.opensearch.script.Script;
 import org.opensearch.search.aggregations.AbstractAggregationBuilder;
 import org.opensearch.search.aggregations.AggregationInitializationException;
@@ -57,7 +58,9 @@
  *
  * @opensearch.internal
  */
-public abstract class ValuesSourceAggregationBuilder<AB extends ValuesSourceAggregationBuilder<AB>> extends AbstractAggregationBuilder<AB> {
+public abstract class ValuesSourceAggregationBuilder<AB extends ValuesSourceAggregationBuilder<AB>> extends AbstractAggregationBuilder<AB>
+    implements
+        WithFieldName {
 
     public static <T> void declareFields(
         AbstractObjectParser<? extends ValuesSourceAggregationBuilder<?>, T> objectParser,
@@ -292,6 +295,11 @@ public String field() {
         return field;
     }
 
+    @Override
+    public String fieldName() {
+        return field();
+    }
+
     /**
      * Sets the script to use for this aggregation.
      */