question: Make imap-flow "sans I/O"?

[duesee]

See https://sans-io.readthedocs.io/ and https://fractalideas.com/blog/sans-io-when-rubber-meets-road/ I very much relate with what is written on the subject.

Examples

• https://github.com/python-hyper/h2/blob/master/examples/plain_sockets/plain_sockets_client.py (Thanks, @epilys)

[jakoschiko]

This might solve problems like #98 or #134 (or at least move the responsibility to the user of imap-flow).

[jakoschiko]

On the other hand, this might remove our ability to force how the stream is handled, e.g. see duesee/imap-proxy#3.

[jakoschiko]

We might want to introduce an interface similar to rustls.