Co-authored-by: Eric Haberkorn <erichaberkorn@gmail.com>
By adding a SpiffeID for server agents, servers can now request a leaf
certificate from the Connect CA.
This new Spiffe ID has a key property: servers are identified by their
datacenter name and trust domain. All servers that share these
attributes will share a ServerURI.
The aim is to use these certificates to verify the server name of ANY
server in a Consul datacenter.
