chore(updater): common GetServers signature

- Log warnings when running outside of CLI mode
- Remove updater CLI bool setting
- Warnings are logged in updating functions

internal/provider/mullvad/updater/servers.go

@@ -6,16 +6,15 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"net/http"
 
 	"github.com/qdm12/gluetun/internal/models"
 )
 
 var ErrNotEnoughServers = errors.New("not enough servers found")
 
-func GetServers(ctx context.Context, client *http.Client, minServers int) (
+func (u *Updater) GetServers(ctx context.Context, minServers int) (
 	servers []models.Server, err error) {
-	data, err := fetchAPI(ctx, client)
+	data, err := fetchAPI(ctx, u.client)
 	if err != nil {
 		return nil, err
 	}

internal/provider/mullvad/updater/updater.go

@@ -0,0 +1,15 @@
+package mullvad
+
+import (
+	"net/http"
+)
+
+type Updater struct {
+	client *http.Client
+}
+
+func New(client *http.Client) *Updater {
+	return &Updater{
+		client: client,
+	}
+}