And here the simple ProxyCallAdapter
that doesn't do anything special, but records the request and it's annotation
content into our map/registry. Everything else is Proxy functionality.
class ProxyCallAdapter<RETURN_TYPE : Any>(
private val adapter: CallAdapter<Any, RETURN_TYPE>,
private val registration: MutableMap<Int, String>,
private val info: String
) : CallAdapter<Any, RETURN_TYPE> {