Maintenance: split each provider in a package

- Fix VyprVPN port
- Fix missing Auth overrides

internal/provider/privateinternetaccess/port.go

@@ -0,0 +1,59 @@
+package privateinternetaccess
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/qdm12/gluetun/internal/constants"
+)
+
+func getPort(tcp bool, encryptionPreset string, customPort uint16) (
+	port uint16, err error) {
+	if customPort == 0 {
+		return getDefaultPort(tcp, encryptionPreset), nil
+	}
+
+	if err := checkPort(customPort, tcp); err != nil {
+		return 0, err
+	}
+
+	return customPort, nil
+}
+
+func getDefaultPort(tcp bool, encryptionPreset string) (port uint16) {
+	if tcp {
+		switch encryptionPreset {
+		case constants.PIAEncryptionPresetNormal:
+			port = 502
+		case constants.PIAEncryptionPresetStrong:
+			port = 501
+		}
+	} else {
+		switch encryptionPreset {
+		case constants.PIAEncryptionPresetNormal:
+			port = 1198
+		case constants.PIAEncryptionPresetStrong:
+			port = 1197
+		}
+	}
+	return port
+}
+
+var ErrInvalidPort = errors.New("invalid port number")
+
+func checkPort(port uint16, tcp bool) (err error) {
+	if tcp {
+		switch port {
+		case 80, 110, 443: //nolint:gomnd
+			return nil
+		default:
+			return fmt.Errorf("%w: %d for protocol TCP", ErrInvalidPort, port)
+		}
+	}
+	switch port {
+	case 53, 1194, 1197, 1198, 8080, 9201: //nolint:gomnd
+		return nil
+	default:
+		return fmt.Errorf("%w: %d for protocol UDP", ErrInvalidPort, port)
+	}
+}