This combats this:
[126624.252775] Route cache is full: consider increasing sysctl net.ipv[4|6].route.max_size.
This used to be fixed manually on edge01.waw, but we forgot to actually
set this in configuration. Whoops
Change-Id: Ibd45f019a9f4d8d6c2bf1db27f438589acaffd77
A customer was missing a static v6 route via their router. Since we
don't want to add them to networking.interfaces.routes.* (as this
restarts the whole scripted network stack in NixOS), we add them to
bird. This requires implementing hscloud.routing.static.
Change-Id: I0a205ed1e1f17a86de43aaf72ab6c2694a069112