[client] Add port forwarding to ssh proxy (#5031)

* Implement port forwarding for the ssh proxy

* Allow user switching for port forwarding

client/server/server.go

@@ -1104,6 +1104,7 @@ func (s *Server) getSSHServerState() *proto.SSHServerState {
 			RemoteAddress: session.RemoteAddress,
 			Command:       session.Command,
 			JwtUsername:   session.JWTUsername,
+			PortForwards:  session.PortForwards,
 		})
 	}