Add factory function to wrap a serial descriptor with a custom name

[Fadenfire]

See #1516 for context.

[sandwwraith]

Great job! Can you please also add to cbor tests your use-case with a custom serializer over byte array?

[Fadenfire]

Unfortunately, I ran into a problem when I tried to add tests for custom CBOR byte strings. When the CBOR encoder/decoder checks for @ByteString on a property it also checks that the descriptor equals ByteArraySerializer().descriptor. Because a wrapped descriptor doesn't have the same name as the original descriptor it doesn't equal the original so the CBOR encoder/decoder will ignore @ByteString on a type with a wrapped descriptor.

Here is the code for the function that CBOR uses to check for @ByteString:

private fun SerialDescriptor.isByteString(index: Int): Boolean {
    val elementDescriptor = getElementDescriptor(index)
    val byteArrayDescriptor = ByteArraySerializer().descriptor

    return (elementDescriptor == byteArrayDescriptor || elementDescriptor == byteArrayDescriptor.nullable) &&
        getElementAnnotations(index).find { it is ByteString } != null
}

The only solution I see is to remove the check for ByteArraySerializer().descriptor in SerialDescriptor.isByteString. There is still a check for ByteArraySerializer().descriptor in encodeSerializableValue so removing the check in SerialDescriptor.isByteString shouldn't cause any problems. I'm not really sure why the check in SerialDescriptor.isByteString is there.

Do you think removing the check for ByteArraySerializer().descriptor in SerialDescriptor.isByteString is safe? Is there a better alternative?

[sandwwraith]

I think it's would be safe to do so, if it is sufficient to do that so custom serializer works. Probably custom serializers just didn't come into mind when this piece of code was written

[Fadenfire]

I have fixed SerialDescriptor.isByteString and added tests for using a custom serializer with CBOR byte strings.

[sandwwraith]

Many thanks! It was a pleasure working with you