[ENHANCEMENTS] SSH Tunnel Forwarding Management

[Cerothen]

Is your feature request related to a problem? Please describe.
Simplify external access for users that are CGNAT'd or do not have access to port forwarding on their local network.

Describe the solution you'd like
SSH tunnel management as outlined in this article. https://www.ssh.com/academy/ssh/tunneling-example

This command connects to a remote host, establishes an encrypted SSH connection then forwards the remote port 8080 and sends it to localhost:80. This could be very useful for users trying to have a non-local public address forward arbitrary ports to the local machine to be used in Zoraxy.

ssh -R 8080:localhost:80 public.example.com

Describe alternatives you've considered
Establish the tunnel and keepalive processes intedendently

[tobychui]

I need to think about this feature. As to me, this raise the same concern for security as the "Service Expose Proxy" feature that I still have no idea how to implement.

I guess the best way to implement this will be asking the admin to upload a list of keys to the zoraxy before allowing ssh -R operations to make sure not everyone can create a tunnel with username / password. Maybe I should ask the security expert @yeungalan for some design opinions.

Also I found this which might be helpful later
https://gist.github.com/0187773933/0f1061d6ada5333dbe462ae2bacd7bbd