feat(test): add comprehensive test coverage for OpenSearch 3 client (#15)

* feat(test): add comprehensive test coverage for OpenSearch 3 client

Add 22 new integration tests to OpenSearch3ClientTest covering
previously untested HTTP action APIs and search query variations:

- Cluster APIs: allocation explain, search shards, cluster state,
  cluster health with index, cluster stats sync
- Indices APIs: segments, shard stores, recovery, indices stats sync
- Document APIs: term vectors, multi term vectors, multi-get with
  source filtering, bulk with mixed operations
- Search queries: source filtering, term/range queries, bool queries,
  exists query, prefix/wildcard queries, IDs query, pagination, sorting
- Admin: simulate pipeline, index template CRUD

https://claude.ai/code/session_018yy83C9EeDpJPn3EXQS66L

* fix(action): correct OpenSearch 3 compatibility issues in HTTP actions and tests

- Use writeVInt instead of writeInt for BroadcastResponse fields in HttpIndicesSegmentsAction
- Remove redundant index_pattern query param in HttpPutIndexTemplateAction (included in body)
- Implement shard counting in HttpRecoveryAction instead of returning zeros
- Update test API calls for OpenSearch 3 (setSelectedFields, setMapping signature)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: marevol

src/main/java/org/codelibs/fesen/client/action/HttpIndicesSegmentsAction.java

@@ -90,9 +90,9 @@ protected IndicesSegmentResponse fromXContent(final XContentParser parser) throw
         // BroadcastResponse wire format: totalShards(int), successfulShards(int), failedShards(int), shardFailures(vint size)
         // Then IndicesSegmentResponse reads: ShardSegments array(vint size)
         try (final ByteArrayStreamOutput out = new ByteArrayStreamOutput()) {
-            out.writeInt(totalShards);
-            out.writeInt(successfulShards);
-            out.writeInt(failedShards);
+            out.writeVInt(totalShards);
+            out.writeVInt(successfulShards);
+            out.writeVInt(failedShards);
             out.writeVInt(0); // no shard failures
             out.writeVInt(0); // no ShardSegments
             return action.getResponseReader().read(out.toStreamInput());

src/main/java/org/codelibs/fesen/client/action/HttpPutIndexTemplateAction.java

@@ -69,9 +69,7 @@ protected CurlRequest getCurlRequest(final PutIndexTemplateRequest request) {
         if (request.cause() != null) {
             curlRequest.param("cause", "");
         }
-        if (request.patterns() != null) {
-            curlRequest.param("index_pattern", String.join(",", request.patterns()));
-        }
+        // patterns are included in the request body via toXContent()
         return curlRequest;
     }
 }

src/main/java/org/codelibs/fesen/client/action/HttpRecoveryAction.java

@@ -58,16 +58,38 @@ protected RecoveryResponse fromXContent(final XContentParser parser) throws IOEx
         }
 
         // The recovery response JSON is {"indexName":{"shards":[{...}]}} with no _shards header.
-        // RecoveryState is complex to parse, so we consume the entire JSON and return an empty response.
+        // RecoveryState is complex to parse, so we count shards and consume the rest.
+        int totalShards = 0;
         while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
             if (token == XContentParser.Token.FIELD_NAME) {
                 // index name
             } else if (token == XContentParser.Token.START_OBJECT) {
-                consumeObject(parser);
+                totalShards += countShardsAndConsume(parser);
             }
         }
 
-        return new RecoveryResponse(0, 0, 0, Collections.emptyMap(), new ArrayList<>());
+        return new RecoveryResponse(totalShards, totalShards, 0, Collections.emptyMap(), new ArrayList<>());
+    }
+
+    protected int countShardsAndConsume(final XContentParser parser) throws IOException {
+        int shardCount = 0;
+        XContentParser.Token token;
+        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
+            if (token == XContentParser.Token.FIELD_NAME && "shards".equals(parser.currentName())) {
+                token = parser.nextToken(); // START_ARRAY
+                if (token == XContentParser.Token.START_ARRAY) {
+                    while (parser.nextToken() != XContentParser.Token.END_ARRAY) {
+                        shardCount++;
+                        consumeObject(parser);
+                    }
+                }
+            } else if (token == XContentParser.Token.START_OBJECT) {
+                consumeObject(parser);
+            } else if (token == XContentParser.Token.START_ARRAY) {
+                consumeObject(parser);
+            }
+        }
+        return shardCount;
     }
 
     protected void consumeObject(final XContentParser parser) throws IOException {