Custom handle_info callbacks

[aram0112]

Hello, hope all is well. I really appreciate that has been put in to bring this library up to speed. I have seen in a few of these issues the sentiment of wanting to maintain the GenServer-like interface. To that end, would it be possible in the library's current state to have custom GenServer handle_info callbacks? I am currently using the latest version pulled from this repository and it seems that all non-message-related handle_info callbacks are consumed by the catch-all handle_info in Jetstream.PullConsumer.Server. Thank you!