Aggregation Metadata does not handle object values properly

[russcam]

The loop to read aggregation metadata

elasticsearch-net/src/Nest/Aggregations/AggregateJsonConverter.cs

Lines 197 to 204 in 53769ae

	while (reader.TokenType != JsonToken.EndObject)
	{
	var key = (string) reader.Value;
	reader.Read();
	var value = reader.Value;
	meta.Add(key, value);
	reader.Read();
	}

does not handle the scenario where the metadata value is an object. In this case, the reader can end up reading the property names of a metadata value object, and adding them as keys within the dictionary e.g.

var response = client.Search<User>(s => s
	.Size(0)
	.Query(q => +q
		.Term(m => m
			.Field(f => f.Badges.First().Name)
            .Value("c#")
        )
    )
	.Aggregations(a => a
		.SignificantTerms("badges", st => st
			.Field(f => f.Badges.First().Name)
            .Meta(m => m
                .Add("meta_1", "value_1")
                .Add("meta_2", 2)
                .Add("meta_3", new { meta_3 = "value_3" })
            )
		)
	)
);

results in the following exception:

System.ArgumentException: An item with the same key has already been added.   at 
System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)   at 
Nest.AggregateJsonConverter.GetMetadata(JsonReader reader)   at
Nest.AggregateJsonConverter.ReadAggregate(JsonReader reader, JsonSerializer serializer)   at 
Nest.AggregateDictionaryConverter.ParseAggregate(JsonReader reader, JsonSerializer serializer, String name, Dictionary`2 dictionary)   at Nest.AggregateDictionaryConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)   at 
Nest.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue)   at 
Nest.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)   at 
Nest.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)   at 
Nest.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)   at 
Nest.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)   at Nest.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)   at Nest.InternalSerializer.Deserialize(Type type, Stream stream)   at 
Nest.InternalSerializer.Deserialize[T](Stream stream)   at 
Elasticsearch.Net.ResponseBuilder.SetBody[TResponse](ApiCallDetails details, RequestData requestData, Stream responseStream, String mimeType) in T:\TeamCity\buildAgent\work\38a00213fd0f22c3\src\Elasticsearch.Net\Transport\Pipeline\ResponseBuilder.cs:line 100   at Elasticsearch.Net.ResponseBuilder.ToResponse[TResponse](RequestData requestData, Exception ex, Nullable`1 statusCode, IEnumerable`1 warnings, Stream responseStream, String mimeType) in T:\TeamCity\buildAgent\work\38a00213fd0f22c3\src\Elasticsearch.Net\Transport\Pipeline\ResponseBuilder.cs:line 25   at Elasticsearch.Net.HttpConnection.Request[TResponse](RequestData requestData) in T:\TeamCity\buildAgent\work\38a00213fd0f22c3\src\Elasticsearch.Net\Connection\HttpConnection.cs:line 180   at Elasticsearch.Net.RequestPipeline.CallElasticsearch[TResponse](RequestData requestData) in T:\TeamCity\buildAgent\work\38a00213fd0f22c3\src\Elasticsearch.Net\Transport\Pipeline\RequestPipeline.cs:line 451   at Elasticsearch.Net.Transport`1.Request[TResponse](HttpMethod method, String path, PostData data, IRequestParameters requestParameters) in T:\TeamCity\buildAgent\work\38a00213fd0f22c3\src\Elasticsearch.Net\Transport\Transport.cs:line 68

because the meta_3 property on the metadata item with key meta_3 is read and is attempted to be added to the meta dictionary.