Fix java doc, add test of WeightedRoundRobinRouting metadata

Signed-off-by: Anshu Agarwal <anshukag@amazon.com>

server/src/main/java/org/opensearch/cluster/metadata/WeightedRoundRobinRoutingMetadata.java

@@ -35,6 +35,7 @@
 public class WeightedRoundRobinRoutingMetadata extends AbstractNamedDiffable<Metadata.Custom> implements Metadata.Custom {
     private static final Logger logger = LogManager.getLogger(WeightedRoundRobinRoutingMetadata.class);
     public static final String TYPE = "wrr_shard_routing";
+    public static final String AWARENESS = "awareness";
     private WRRWeights wrrWeight;
 
     public WRRWeights getWrrWeight() {
@@ -140,7 +141,7 @@ public XContentBuilder toXContent(XContentBuilder builder, ToXContent.Params par
     }
 
     public static void toXContent(WRRWeights wrrWeight, XContentBuilder builder) throws IOException {
-        builder.startObject("awareness");
+        builder.startObject(AWARENESS);
         builder.startObject(wrrWeight.attributeName());
         for (Map.Entry<String, Object> entry : wrrWeight.weights().entrySet()) {
             builder.field(entry.getKey(), entry.getValue());

server/src/main/java/org/opensearch/cluster/routing/WeightedRoundRobin.java

@@ -10,7 +10,10 @@
 
 import java.util.ArrayList;
 import java.util.List;
-
+/**
+ * Weighted Round Robin Scheduling policy
+ *
+ */
 public class WeightedRoundRobin<T> {
 
     private List<WeightedRoundRobin.Entity<T>> entities;

server/src/test/java/org/opensearch/cluster/metadata/WeightedRoundRobinRoutingMetadataTests.java

@@ -0,0 +1,37 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.cluster.metadata;
+
+import org.opensearch.cluster.routing.WRRWeights;
+import org.opensearch.common.xcontent.XContentParser;
+import org.opensearch.test.AbstractXContentTestCase;
+
+import java.io.IOException;
+import java.util.Map;
+
+public class WeightedRoundRobinRoutingMetadataTests extends AbstractXContentTestCase<WeightedRoundRobinRoutingMetadata> {
+    @Override
+    protected WeightedRoundRobinRoutingMetadata createTestInstance() {
+        Map<String, Object> weights = Map.of("a", "1", "b", "1", "c", "0");
+        WRRWeights wrrWeights = new WRRWeights("zone", weights);
+        WeightedRoundRobinRoutingMetadata wrrMetadata = new WeightedRoundRobinRoutingMetadata(wrrWeights);
+        return wrrMetadata;
+    }
+
+    @Override
+    protected WeightedRoundRobinRoutingMetadata doParseInstance(XContentParser parser) throws IOException {
+        return WeightedRoundRobinRoutingMetadata.fromXContent(parser);
+    }
+
+    @Override
+    protected boolean supportsUnknownFields() {
+        return false;
+    }
+
+}