ConverterToOptional
@RequiresOptIn(message = "When creating an Arguments class, you must use one of the converter functions starting with "optional" instead. Otherwise, if you know what you're doing (or you're writing your own converter functions), please feel free to opt-in.
For example, instead of `boolean(...).toOptional()`, consider `optionalBoolean(...)`.
Failure to register your converters this way may result in strange or broken behaviour.")
Opt-in annotation for .toOptional() converter functions.