With this patch, the relay can parse and respond to allocation requests. I
ran some basics tests against https://icetest.info/ and implemented a
regression test as a result of the logged data.
In writing this, I also had to slightly change the design of `Server`
(as expected). Event handlers for incoming data now do not return a
message directly. Instead, the caller is responsible to drain `Command`s
from it.
When creating an allocation, we need to start listening on a new port.
This needs to happen outside the `Server` as I am going for a sans-IO
style. We emit a `Command` that instructs the main event loop to listen
on a new port. Any incoming data on that port will be forwarded to the
`Server`.
At the moment, this incoming data is just dropped. This is actually
standards-compliant because we cannot handle binding requests yet which
would allow this data to be forwarded to the client.
In some areas, the code is still a bit rough but I expect to iron those
things out as we go along.
This is an alternative to https://github.com/firezone/firezone/pull/1602
that implements the server using a library I've found called
`stun_codec`.
It already has support for parsing a variety of attributes.
The following is a nice website to test some of the functionality:
https://icetest.info/
The server is still listening on:
`ec2-3-89-112-240.compute-1.amazonaws.com:3478`.
