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

internal/provider/utils/portforward.go

@@ -0,0 +1,27 @@
+package utils
+
+import (
+	"net/http"
+	"net/netip"
+)
+
+// PortForwardObjects contains fields that may or may not need to be set
+// depending on the port forwarding provider code.
+type PortForwardObjects struct {
+	// Logger is a logger, used by both Private Internet Access and ProtonVPN.
+	Logger Logger
+	// Gateway is the VPN gateway IP address, used by Private Internet Access
+	// and ProtonVPN.
+	Gateway netip.Addr
+	// Client is used to query the VPN gateway for Private Internet Access.
+	Client *http.Client
+	// ServerName is used by Private Internet Access for port forwarding,
+	// and to look up the server data from storage.
+	// TODO use server data directly to remove storage dependency for port
+	// forwarding implementation.
+	ServerName string
+}
+
+type Routing interface {
+	VPNLocalGatewayIP(vpnInterface string) (gateway netip.Addr, err error)
+}