make connected-server address nicer

[warner]

#2818 changed the "Connected Servers" table on the welcome page, to make the "Address" column show the full connection hint list, instead of the one address returned by rref.getPeer(). This makes e.g. Tor connections over unix-domain SOCKS sockets nicer, but makes plain TCP hints (especially when the target advertises multiple connection hints) more verbose.

[Foolscap#267 ​https://foolscap.lothar.com/trac/ticket/267] is about adding a new RemoteReference API that could give us nicer information. Specifically, it would tell us *how* the connection was made (which handler, which hint, maybe which IP address the hostname resolved to), rather than just the intended target of the FURL. That could provide some assurance that we really did use Tor, for example.

So this ticket is about adding IServer.get_connection_info() to NativeStorageServer, which delegates to the new Foolscap API, and then changing allmydata.web.root.Root.render_service_row() to use the new information instead of server.get_remote_host() (which could probably be removed altogether).

I'm tenatively scheduling this for the 1.12 milestone, because the default tub.location=AUTO yields hints for every interface, which makes this Welcome-page display pretty ugly, and I'd like to see that fixed. But it depends upon the new Foolscap API, which I haven't finished specing out yet, so I stand prepared to drop this from 1.12 if that doesn't happen soon.

[warner]

See ​https://github.com/tahoe-lafs/tahoe-lafs/pull/383 . I think we're going to make some UI tweaks before landing it.

[Brian Warner <warner@…>]

In fe1df17d/trunk:

Merge branch '2490-connection-info'

This updates the WUI welcome page with more information about each server
connection (and the introducer connection): which handler is being used, how
the connection process is going, and/or why it failed.

Closes ticket:2819