Add serve_uds to axum-extra

[davidpdrsn]

axum::serve intentionally only supports TcpListener because it greatly simplifies the API. However that means serving over a unix domain socket requires a lot of boilerplate.

We should add a dedicated serve_uds function to axum-extra that makes that easier. I should be possible to more or less copy axum::serve and use Tokio's UnixListener instead.

[vi]

Will it also make serving connections over arbitrary AsyncRead+AsyncWrite pairs easier?

[davidpdrsn]

No. hyper 0.14's server used to allow that but it leads to nasty trait bounds which I really want to avoid.

[fundon]

A trait for a listener already exists: Listener

[davidpdrsn]

Oh neat! That might be worth trying to use.

[jplatte]

So I guess #2479 will work for UDS and we don't actually want to add a separate serve_uds?

[davidpdrsn]

Yes exactly!