support attributes in System.Text.Json.Serialization Namespace

[zijianhuang]

https://learn.microsoft.com/en-us/dotnet/api/system.text.json.serialization

Need to further study vendor recommended ways: https://www.newtonsoft.com/json/help/html/JsonObjectAttributeOptIn.htm https://github.com/dotnet/runtime/issues/30180

Need to clarify Microsoft's position.

DataContractAttribute is primarily for WCF and DataContract serializer. WCF service is not a built-in framework in .NET. Even though DataContractAttribute is universal, not really exclusive to WCF.

[zijianhuang]

wait for response from https://github.com/dotnet/docs/issues/38687