chore(portforward): move vpn gateway obtention within port forwarding service

internal/portforward/service/interfaces.go

@@ -2,6 +2,9 @@ package service
 
 import (
 	"context"
+	"net/netip"
+
+	"github.com/qdm12/gluetun/internal/provider/utils"
 )
 
 type PortAllower interface {
@@ -9,8 +12,19 @@ type PortAllower interface {
 	RemoveAllowedPort(ctx context.Context, port uint16) (err error)
 }
 
+type Routing interface {
+	VPNLocalGatewayIP(vpnInterface string) (gateway netip.Addr, err error)
+}
+
 type Logger interface {
 	Info(s string)
 	Warn(s string)
 	Error(s string)
 }
+
+type PortForwarder interface {
+	Name() string
+	PortForward(ctx context.Context, objects utils.PortForwardObjects) (
+		port uint16, err error)
+	KeepPortForward(ctx context.Context, objects utils.PortForwardObjects) (err error)
+}