PIA nextgen portforward (#242)

* Split provider/pia.go in piav3.go and piav4.go
* Change port forwarding signature
* Enable port forwarding parameter for PIA v4
* Fix VPN gateway IP obtention
* Setup HTTP client for TLS with custom cert
* Error message for regions not supporting pf

internal/provider/utils.go

@@ -0,0 +1,29 @@
+package provider
+
+import (
+	"context"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+)
+
+func tryUntilSuccessful(ctx context.Context, logger logging.Logger, fn func() error) {
+	const retryPeriod = 10 * time.Second
+	for {
+		err := fn()
+		if err == nil {
+			break
+		}
+		logger.Error(err)
+		logger.Info("Trying again in %s", retryPeriod)
+		timer := time.NewTimer(retryPeriod)
+		select {
+		case <-timer.C:
+		case <-ctx.Done():
+			if !timer.Stop() {
+				<-timer.C
+			}
+			return
+		}
+	}
+}