Loops and HTTP control server rework (#308)

- CRUD REST HTTP server
- `/v1` HTTP server prefix
- Retrocompatible with older routes (redirects to v1 or handles the requests directly)
- DNS, Updater and Openvpn refactored to have a REST-like state with new methods to change their states synchronously
- Openvpn, Unbound and Updater status, see #287

internal/settings/updater.go

@@ -0,0 +1,59 @@
+package settings
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/params"
+)
+
+type Updater struct {
+	Period     time.Duration `json:"period"`
+	DNSAddress string        `json:"dns_address"`
+	Cyberghost bool          `json:"cyberghost"`
+	Mullvad    bool          `json:"mullvad"`
+	Nordvpn    bool          `json:"nordvpn"`
+	PIA        bool          `json:"pia"`
+	Privado    bool          `json:"privado"`
+	Purevpn    bool          `json:"purevpn"`
+	Surfshark  bool          `json:"surfshark"`
+	Vyprvpn    bool          `json:"vyprvpn"`
+	Windscribe bool          `json:"windscribe"`
+	// The two below should be used in CLI mode only
+	Stdout bool `json:"-"` // in order to update constants file (maintainer side)
+	CLI    bool `json:"-"`
+}
+
+// GetUpdaterSettings obtains the server updater settings using the params functions.
+func GetUpdaterSettings(paramsReader params.Reader) (settings Updater, err error) {
+	settings = Updater{
+		Cyberghost: true,
+		Mullvad:    true,
+		Nordvpn:    true,
+		PIA:        true,
+		Purevpn:    true,
+		Surfshark:  true,
+		Vyprvpn:    true,
+		Windscribe: true,
+		Stdout:     false,
+		CLI:        false,
+		DNSAddress: "127.0.0.1",
+	}
+	settings.Period, err = paramsReader.GetUpdaterPeriod()
+	if err != nil {
+		return settings, err
+	}
+	return settings, nil
+}
+
+func (s *Updater) String() string {
+	if s.Period == 0 {
+		return "Server updater settings: disabled"
+	}
+	settingsList := []string{
+		"Server updater settings:",
+		fmt.Sprintf("Period: %s", s.Period),
+	}
+	return strings.Join(settingsList, "\n|--")
+}