IP_STATUS_FILE and routing improvements (#130)

- Obtains VPN public IP address from routing table
- Logs and writes VPN Public IP address to `/ip` as soon as VPN is up
- Obtain port forward, logs it and writes it as soon as VPN is up
- Routing fully refactored and tested
- Routing reads from `/proc/net/route`
- Routing mutates the routes using `ip route ...`

internal/params/params.go

@@ -32,6 +32,7 @@ type ParamsReader interface {
 	GetUID() (uid int, err error)
 	GetGID() (gid int, err error)
 	GetTimezone() (timezone string, err error)
+	GetIPStatusFilepath() (filepath models.Filepath, err error)
 
 	// Firewall getters
 	GetExtraSubnets() (extraSubnets []net.IPNet, err error)