Want API endpoints for full switch router information base (RIB)

Right now, we have the ability to list static routes per port and show imported BGP prefixes per switch through the Omicron API. But for complex networking setups, this does not tell the whole story. Routes have a set of attributes that all come together under the best path algorithm to determine what path or paths are considered optimal in the presence of multiple path choices. Only paths that are in the optimal set get installed into the forwarding plane.

The mgd API provides a way to get at the information that the best path algorithm is using for selection as shown through the CLI invocation below.

root@oxz_switch:~# mgadm bgp status selected
BGP Routes
=============
Prefix        Nexthop       Local Pref  Origin AS  Peer ID        MED   AS Path         Stale
0.0.0.0/0     169.254.10.1  None        64500      192.168.1.168  None  [64500, 64510]  None
2.0.1.0/24    169.254.50.1  Some(20)    64501      192.168.1.176  None  [64501, 64570]  None
[...]

There is also a mgadm bgp status imported command that allows operators to see the delta between imported and selected routes. (Note that bgp here is a bit of a misnomer as this started out as just a BGP CLI command, but now includes static routing, so this should be more like mgadm rib status selected and mgadm rib status imported.)

All this information should be available to the operator through the Omicron API.

Start by reading rdb/src/bestpath.rs and the existing Omicron API endpoints for static routes and imported BGP prefixes. Compare the mgadm bgp status selected and imported outputs, including the route attributes used by the best path algorithm. Done means operators can access equivalent full RIB information through the Omicron API, with selected and imported route views.