Type safe serialization of primitives and System.Type

[hakito]

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EnsureRoundtrip emits tags for objects when needed. But it does not force emission of tags for primitives.

For example the class

class Container
{
    public object Data { get; set; } = 123L;
}

will be deserialized as string "123".

I could bypass the problem by appending a custom ChainedEventEmitter after the TypeAssigningEventEmitter.

However It was still not possible to properly deserialize the container when data was assigned an instance of System.Type. For example container.Data = typeof(long) is deserialized also as string because the SystemTypeConverter bypassed the ChainedEventEmitter and also does not emit a tag:

https://github.com/aaubry/YamlDotNet/blob/5ec2dd75704d6dced41c0d49ff5528f3797d1068/YamlDotNet/Serialization/Converters/SystemTypeConverter.cs#L30

I'd suggest to add a method like WithSystemTypeTagPrefix(string) to the serialization builder classes and always emit tags when the runtime type is not equal to the declared type.