RequestResponseSerializer.Deserialize cannot deserialize "preserve_original" : "true"

[gobaaspudden]

Elastic.Clients.Elasticsearch version: 8.1.1

Elasticsearch version: 8.7.1

.NET runtime version: 4.8

Operating system version: Windows 11

Description of the problem including expected versus actual behavior:
There is a missmatch between elasticsearch json and the client deserializer when creating an index with
settings - analysis - filter - custom_ascii_folding - preserve_original : true
Expected behavior: Add index and read index without error.
Actual behavior: Reading index will result in json parse exception

Steps to reproduce:

1. Add index with filter tokenfilter tf -> tf.AsciiFolding("custom_ascii_folding", e => e.PreserveOriginal(true));
2. Get Index - Indices.Get(new GetIndexRequest(Indices.All))
3. Exception occurs

Expected behavior
Elastic should serialize PreserveOriginal as bool ( "preserve_original": true )
or RequestResponseSerializer should be able to handle conversion from string "true" to bool.

Provide DebugInformation (if relevant):

Here is the GetIndex response from elastic 8.7.1:
{"article-test-en-us":{"aliases":{},"mappings":{"properties":{"categories":{"type":"keyword"},"content":{"type":"text","index_options":"offsets","analyzer":"custom_html"},"defaultViewOriginContexts":{"type":"keyword"},"statistics":{"type":"nested","properties":{"popularity":{"type":"double"},"role":{"type":"keyword"},"viewOriginContext":{"type":"keyword"}}},"title":{"type":"text","index_options":"offsets","analyzer":"custom_html"}}},"settings":{"index":{"routing":{"allocation":{"include":{"_tier_preference":"data_content"}}},"number_of_shards":"1","provided_name":"article-test-en-us","creation_date":"1687162213728","analysis":**_{"filter":{"custom_ascii_folding":{"type":"asciifolding","preserve_original":"true"},_**"english_stemmer":{"type":"stemmer","language":"english"},"english_stop":{"type":"stop","stopwords":"_english_"}},"analyzer":{"custom_html":{"filter":["lowercase","custom_ascii_folding","english_stop","english_stemmer"],"char_filter":["custom_html_strip"],"type":"custom","tokenizer":"standard"}},"char_filter":{"custom_html_strip":{"type":"html_strip"}}},"number_of_replicas":"1","uuid":"Zzyhj9S9QfeLBgozuC0H3A","version":{"created":"8070199"}}}}}

RequestResponseSerializer.Deserialize()

System.Text.Json.JsonException: The JSON value could not be converted to System.Nullable1[System.Boolean]. Path: $.preserve_original | LineNumber: 2 | BytePositionInLine: 42. ---> System.InvalidOperationException: Cannot get the value of a token type 'String' as a boolean.`

Stack Trace: 
ThrowHelper.ThrowInvalidOperationException_ExpectedBoolean(JsonTokenType tokenType)
Utf8JsonReader.GetBoolean()
BooleanConverter.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options)
NullableConverter1.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options) JsonPropertyInfo1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
ObjectDefaultConverter1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value) JsonConverter1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
JsonConverter1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state) --- End of inner exception stack trace --- ThrowHelper.ReThrowWithPath(ReadStack& state, Utf8JsonReader& reader, Exception ex) <35 more frames...> JsonSerializer.Deserialize[TValue](Utf8JsonReader& reader, JsonSerializerOptions options) ResolvableDictionaryResponseConverterInner3.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options) line 74
JsonConverter1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value) JsonConverter1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
JsonSerializer.ReadCore[TValue](Utf8JsonReader& reader, JsonTypeInfo jsonTypeInfo, ReadStack& state)
JsonSerializer.ContinueDeserialize[TValue](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonTypeInfo jsonTypeInfo)
JsonSerializer.ReadFromStream[TValue](Stream utf8Json, JsonTypeInfo jsonTypeInfo)
JsonSerializer.Deserialize[TValue](Stream utf8Json, JsonSerializerOptions options)

[gobaaspudden]

I discovered the same issue for settings - index- lifecycle - "indexing_complete" : "true"

[stevejgordon]

This looks like a spec issue which needs to be addressed to support these properties potentially being returned as strings rather than raw boolean values.