Reverse tunnels are now first class citizens of teleport.
There's no longer static configuration for reverse tunnel agents
in the config. Instead, admins can add and remove reverse tunnels
using tctl reversetunnel (hidden) commands.
* tctl reversetunnel ls
lists reverse tunnels
* tctl reversetunnel upsert a.example.com 10.0.0.4:2023,10.0.0.5:2033 --ttl=10m
updates or inserts reverse tunnel for 10 minutes
* tctl reversetunnel del a.example.com
deletes a reverse tunnel
Teleport proxies watch changes in the reverse tunnels on the backend and
spin up / spin down reverse tunnels according to these changes.