Probably unnecessary Array copy

[samuelorji]

Hi,

Is there any reason why we can't call ByteString.fromArrayUnsafe here instead of calling apply on ByteString which should save us an array copy .

We already do ByteString.fromArrayUnsafe for the JsValue writeable here.

[PromanSEW]

Please provide PR to fix this behaviour so :)

[maxcom]

Array is a mutable structure and it is not safe to assume that it won't change. JsValue case is different, because we know that Json.toBytes allocates new array on each call.