Type of PR

Hello! While reviewing the Kotlin part of Armeria, I noticed that in the FlowResponseConverterFunctionProvider class, there's an extension function for Type used in the createResponseConverterFunction() function of DelegatingResponseConverterFunctionProvider. The toClass() function returns a type of Class<*>?.

In the past, when working with Kotlin, I found it beneficial to define extension functions that return nullable values with names following the toXXXOrNull() pattern. This made the code more understandable for me and my teammates, especially during maintenance.

Since the extension function is defined just below createResponseConverterFunction(), it may lead to questions like "Why use toClass()?.let here?" Adding OrNull to the function name can make the code more readable.

I understand that naming conventions can vary among teams, and it may not be a critical issue. However, if you find the suggestion helpful, I'd appreciate it if you could consider applying the change.

private fun Type.toClassOrNull(): Class<*>? =
    when (this) {
        is ParameterizedType -> this.rawType as Class<*>
        is Class<*> -> this
        else -> null
    }