Maintenance: split each provider in a package

- Fix VyprVPN port
- Fix missing Auth overrides

internal/provider/privateinternetaccess/httpclient.go

@@ -0,0 +1,57 @@
+package privateinternetaccess
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/constants"
+)
+
+var (
+	ErrParseCertificate = errors.New("cannot parse X509 certificate")
+)
+
+func newHTTPClient(serverName string) (client *http.Client, err error) {
+	certificateBytes, err := base64.StdEncoding.DecodeString(constants.PIACertificateStrong)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %s", ErrParseCertificate, err)
+	}
+	certificate, err := x509.ParseCertificate(certificateBytes)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %s", ErrParseCertificate, err)
+	}
+
+	//nolint:gomnd
+	transport := &http.Transport{
+		// Settings taken from http.DefaultTransport
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: (&net.Dialer{
+			Timeout:   30 * time.Second,
+			KeepAlive: 30 * time.Second,
+		}).DialContext,
+		ForceAttemptHTTP2:     true,
+		MaxIdleConns:          100,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+	}
+	rootCAs := x509.NewCertPool()
+	rootCAs.AddCert(certificate)
+	transport.TLSClientConfig = &tls.Config{
+		RootCAs:    rootCAs,
+		MinVersion: tls.VersionTLS12,
+		ServerName: serverName,
+	}
+
+	const httpTimeout = 30 * time.Second
+	return &http.Client{
+		Transport: transport,
+		Timeout:   httpTimeout,
+	}, nil
+}