Add support for listening on AF_UNIX

[jrb0001]

AF_UNIX uses filesystem paths instead of address+port pairs for socket addresses which makes it much easier to avoid conflicts if you run multiple services on the same machine.

tide 0.12.0 seems to support it with the http+unix:///path scheme: https://docs.rs/tide/0.12.0/tide/listener/trait.ToListener.html#strings-supported-only-on-cfgunix-platforms

I am planning to run alexandrie behind a reverse-proxy (which also does TLS termination) so this would be a useful feature for me.

[Hirevo]

Hello, thanks for filing this issue.

I agree that the configuration file right now is not flexible enough to permit this.
I think I'll be fixing this, right after making the upgrade to Tide 0.12 (it is currently sitting on 0.10).

And I think I'll be changing the configuration to go from this:

[general]
addr = "0.0.0.0"
port = 3000

to this:

[general]
bind_address = "0.0.0.0:3000"
# or
bind_address = "http+unix:///path"
# or any other address that Tide knows how to turn into a `Listener`

Would that correctly fit your use-case ?

[jrb0001]

Yes, that's exactly what I need and I don't think there is really another way to do it. This should also fix listening on link-local IPv6 addresses, assuming tide handles them correctly.