Maintenance: split each provider in a package

- Fix VyprVPN port
- Fix missing Auth overrides

internal/provider/surfshark/portforward.go

@@ -0,0 +1,17 @@
+package surfshark
+
+import (
+	"context"
+	"net"
+	"net/http"
+
+	"github.com/qdm12/gluetun/internal/firewall"
+	"github.com/qdm12/golibs/logging"
+	"github.com/qdm12/golibs/os"
+)
+
+func (s *Surfshark) PortForward(ctx context.Context, client *http.Client,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP,
+	fw firewall.Configurator, syncState func(port uint16) (pfFilepath string)) {
+	panic("port forwarding is not supported for Surfshark")
+}