Server example

[tsurdevson]

Hi! First of all, thanks for all the work putting this library together! It's so cool to see new things like Ratatui games run over ssh.

I've found the server-side examples a little lacking. Say I want to implement a server that does exec requests (the "commands" wouldn't have to be system commands, could be application level things), I'm having a little trouble mapping the existing echo server example to that scenario.

In particular, for sending/receiving data (what would read/write to stdin/stdout/stderr for the client) to such an exec requests, which one of these should I use? Handler::data, Session::handle().data, Channel::make_reader/make_writer, Channel::into_stream

All of these seem to give ways of reading and/or writing, but I don't quite understand when to use which one. Some kind of example would go a long way here I think.

I'm happy to try to put one together, provided I get some help here in wrapping my head around 👆