chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/provider/surfshark/updater/updater.go

@@ -4,22 +4,17 @@ import (
 	"net/http"
 
 	"github.com/qdm12/gluetun/internal/provider/common"
-	"github.com/qdm12/gluetun/internal/updater/unzip"
 )
 
 type Updater struct {
 	client    *http.Client
-	unzipper  unzip.Unzipper
+	unzipper  common.Unzipper
 	presolver common.ParallelResolver
-	warner    Warner
+	warner    common.Warner
 }
 
-type Warner interface {
-	Warn(s string)
-}
-
-func New(client *http.Client, unzipper unzip.Unzipper,
-	warner Warner) *Updater {
+func New(client *http.Client, unzipper common.Unzipper,
+	warner common.Warner) *Updater {
 	return &Updater{
 		client:    client,
 		unzipper:  unzipper,