Additional UTF8Json overloads, consolidate how we tell it to write/serialize.

src/Elasticsearch.Net/Serialization/DiagnosticsSerializerProxy.cs

@@ -35,9 +35,10 @@ public SerializerRegistrationInformation(Type type, string purpose)
 	/// <summary>
 	/// Wraps configured serializer so that we can emit diagnostics per configured serializer.
 	/// </summary>
-	internal class DiagnosticsSerializerProxy : IElasticsearchSerializer, IInternalSerializerWithFormatter
+	internal class DiagnosticsSerializerProxy : IElasticsearchSerializer, IInternalSerializer
 	{
 		private readonly IElasticsearchSerializer _serializer;
+		private readonly bool _wrapsUtf8JsonSerializer;
 		private readonly SerializerRegistrationInformation _state;
 		private readonly IJsonFormatterResolver _formatterResolver;
 		private static DiagnosticSource DiagnosticSource { get; } = new DiagnosticListener(DiagnosticSources.Serializer.SourceName);
@@ -46,11 +47,23 @@ public DiagnosticsSerializerProxy(IElasticsearchSerializer serializer, string pu
 		{
 			_serializer = serializer;
 			_state = new SerializerRegistrationInformation(serializer.GetType(), purpose);
-			if (serializer is IInternalSerializerWithFormatter withFormatter)
-				_formatterResolver = withFormatter.FormatterResolver;
+			if (serializer is IInternalSerializer s && s.TryGetJsonFormatter(out var formatterResolver))
+			{
+				_formatterResolver = formatterResolver;
+				_wrapsUtf8JsonSerializer = true;
+			}
+			else
+			{
+				_formatterResolver = null;
+				_wrapsUtf8JsonSerializer = false;
+			}
 		}
 
-		public IJsonFormatterResolver FormatterResolver => _formatterResolver;
+		public bool TryGetJsonFormatter(out IJsonFormatterResolver formatterResolver)
+		{
+			formatterResolver = _formatterResolver;
+			return _wrapsUtf8JsonSerializer;
+		}
 
 		public object Deserialize(Type type, Stream stream)
 		{

src/Elasticsearch.Net/Serialization/ElasticsearchSerializerExtensions.cs

@@ -1,9 +1,23 @@
 using Elasticsearch.Net.Extensions;
+using Elasticsearch.Net.Utf8Json;
 
 namespace Elasticsearch.Net
 {
 	public static class ElasticsearchSerializerExtensions
 	{
+		internal static void SerializeUsingWriter<T>(this IElasticsearchSerializer serializer, ref JsonWriter writer, T body, IConnectionConfigurationValues settings, SerializationFormatting formatting)
+		{
+			if (serializer is IInternalSerializer s && s.TryGetJsonFormatter(out var formatterResolver))
+			{
+				JsonSerializer.Serialize(ref writer, body, formatterResolver);
+				return;
+			}
+
+			var memoryStreamFactory = settings.MemoryStreamFactory;
+			var bodyBytes = serializer.SerializeToBytes(body, memoryStreamFactory, formatting);
+			writer.WriteRaw(bodyBytes);
+		}
+
 		/// <summary>
 		/// Extension method that serializes an instance of <typeparamref name="T"/> to a byte array.
 		/// </summary>
@@ -65,5 +79,6 @@ public static string SerializeToString<T>(
 				return ms.Utf8String();
 			}
 		}
+
 	}
 }

src/Elasticsearch.Net/Serialization/IInternalSerializerWithFormatter.cs

@@ -1,9 +1,10 @@
 using Elasticsearch.Net.Utf8Json;
 
-namespace Elasticsearch.Net 
+namespace Elasticsearch.Net
 {
-	internal interface IInternalSerializerWithFormatter
+	internal interface IInternalSerializer
 	{
-		IJsonFormatterResolver FormatterResolver { get; }
+		bool TryGetJsonFormatter(out IJsonFormatterResolver formatterResolver);
 	}
-}
+
+}

src/Elasticsearch.Net/Serialization/LowLevelRequestResponseSerializer.cs

@@ -7,7 +7,7 @@
 
 namespace Elasticsearch.Net
 {
-	public class LowLevelRequestResponseSerializer : IElasticsearchSerializer
+	public class LowLevelRequestResponseSerializer : IElasticsearchSerializer, IInternalSerializer
 	{
 		public static readonly LowLevelRequestResponseSerializer Instance = new LowLevelRequestResponseSerializer();
 
@@ -30,5 +30,11 @@ public Task SerializeAsync<T>(T data, Stream writableStream, SerializationFormat
 			CancellationToken cancellationToken = default
 		) =>
 			JsonSerializer.SerializeAsync(writableStream, data, ElasticsearchNetFormatterResolver.Instance);
+
+		bool IInternalSerializer.TryGetJsonFormatter(out IJsonFormatterResolver formatterResolver)
+		{
+			formatterResolver = ElasticsearchNetFormatterResolver.Instance;
+			return true;
+		}
 	}
 }