Maintenance: split each provider in a package

- Fix VyprVPN port
- Fix missing Auth overrides

internal/provider/protonvpn/port.go

@@ -0,0 +1,41 @@
+package protonvpn
+
+import (
+	"errors"
+	"fmt"
+)
+
+func getPort(tcp bool, customPort uint16) (port uint16, err error) {
+	if customPort == 0 {
+		const defaultTCPPort, defaultUDPPort = 443, 1194
+		if tcp {
+			return defaultTCPPort, nil
+		}
+		return defaultUDPPort, nil
+	}
+
+	if err := checkPort(customPort, tcp); err != nil {
+		return 0, err
+	}
+
+	return customPort, nil
+}
+
+var ErrInvalidPort = errors.New("invalid port number")
+
+func checkPort(port uint16, tcp bool) (err error) {
+	if tcp {
+		switch port {
+		case 443, 5995, 8443: //nolint:gomnd
+			return nil
+		default:
+			return fmt.Errorf("%w: %d for protocol TCP", ErrInvalidPort, port)
+		}
+	}
+	switch port {
+	case 80, 443, 1194, 4569, 5060: //nolint:gomnd
+		return nil
+	default:
+		return fmt.Errorf("%w: %d for protocol UDP", ErrInvalidPort, port)
+	}
+}