DATAES-988 Allow specifying max results in NativeSearchQueryBuilder

Original PR: #561 

Add a withMaxResults method to NativeSearchQueryBuilder for specifying the maxResults
on the built Query. This is common for aggregation queries where search hits are not
needed.

Having the builder method for setting maxResults is a minor ergonomic improvement, e.g.

NativeSearchQuery searchQuery = NativeSearchQueryBuilder()
        .withQuery(matchAllQuery())
        .addAggregation(terms("examples").field("example"))
        .withMaxResults(0)
        .build();

versus what was required before:

NativeSearchQuery searchQuery = NativeSearchQueryBuilder()
        .withQuery(matchAllQuery())
        .addAggregation(terms("examples").field("example"))
        .build();
searchQuery.setMaxResults(0);

Author: kilink

src/main/java/org/springframework/data/elasticsearch/core/query/NativeSearchQueryBuilder.java

@@ -66,6 +66,7 @@ public class NativeSearchQueryBuilder {
 	@Nullable private SearchType searchType;
 	@Nullable private IndicesOptions indicesOptions;
 	@Nullable private String preference;
+	@Nullable private Integer maxResults;
 
 	public NativeSearchQueryBuilder withQuery(QueryBuilder queryBuilder) {
 		this.queryBuilder = queryBuilder;
@@ -167,6 +168,11 @@ public NativeSearchQueryBuilder withPreference(String preference) {
 		return this;
 	}
 
+	public NativeSearchQueryBuilder withMaxResults(Integer maxResults) {
+		this.maxResults = maxResults;
+		return this;
+	}
+
 	public NativeSearchQuery build() {
 
 		NativeSearchQuery nativeSearchQuery = new NativeSearchQuery(queryBuilder, filterBuilder, sortBuilders,
@@ -218,10 +224,15 @@ public NativeSearchQuery build() {
 		if (indicesOptions != null) {
 			nativeSearchQuery.setIndicesOptions(indicesOptions);
 		}
+
 		if (preference != null) {
 			nativeSearchQuery.setPreference(preference);
 		}
 
+		if (maxResults != null) {
+			nativeSearchQuery.setMaxResults(maxResults);
+		}
+
 		return nativeSearchQuery;
 	}
 }

src/test/java/org/springframework/data/elasticsearch/core/aggregation/ElasticsearchTemplateAggregationTests.java

@@ -118,6 +118,7 @@ public void shouldReturnAggregatedResponseForGivenSearchQuery() {
 				.withQuery(matchAllQuery()) //
 				.withSearchType(SearchType.DEFAULT) //
 				.addAggregation(terms("subjects").field("subject")) //
+				.withMaxResults(0) //
 				.build();
 		// when
 		SearchHits<ArticleEntity> searchHits = operations.search(searchQuery, ArticleEntity.class,
@@ -127,6 +128,7 @@ public void shouldReturnAggregatedResponseForGivenSearchQuery() {
 		// then
 		assertThat(aggregations).isNotNull();
 		assertThat(aggregations.asMap().get("subjects")).isNotNull();
+		assertThat(searchHits.hasSearchHits()).isFalse();
 	}
 
 	/**