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/logging/duration.go

@@ -0,0 +1,29 @@
+package logging
+
+import (
+	"fmt"
+	"time"
+)
+
+func FormatDuration(duration time.Duration) string {
+	switch {
+	case duration < time.Minute:
+		seconds := int(duration.Round(time.Second).Seconds())
+		if seconds < 2 {
+			return fmt.Sprintf("%d second", seconds)
+		}
+		return fmt.Sprintf("%d seconds", seconds)
+	case duration <= time.Hour:
+		minutes := int(duration.Round(time.Minute).Minutes())
+		if minutes == 1 {
+			return "1 minute"
+		}
+		return fmt.Sprintf("%d minutes", minutes)
+	case duration < 48*time.Hour:
+		hours := int(duration.Truncate(time.Hour).Hours())
+		return fmt.Sprintf("%d hours", hours)
+	default:
+		days := int(duration.Truncate(time.Hour).Hours() / 24)
+		return fmt.Sprintf("%d days", days)
+	}
+}