https://docs.microsoft.com/ja-jp/dotnet/api/system.text.json.serialization.jsonconverterattribute.createconverter?view=net-10.0
JsonConverterAttribute.CreateConverter(Type) Method (System.Text.Json.Serialization) | Microsoft...
When overridden in a derived class and ConverterType is null, allows the derived class to create a JsonConverter in order to pass additional state.
json serializationtypemethodsystemtext