chore(all): return concrete types, accept interfaces

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

internal/cli/openvpnconfig.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"strings"
@@ -10,18 +11,18 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/provider"
 	"github.com/qdm12/gluetun/internal/storage"
-	"github.com/qdm12/gluetun/internal/updater/unzip"
 )
 
-type OpenvpnConfigMaker interface {
-	OpenvpnConfig(logger OpenvpnConfigLogger, source sources.Source) error
-}
-
 type OpenvpnConfigLogger interface {
 	Info(s string)
 	Warn(s string)
 }
 
+type Unzipper interface {
+	FetchAndExtract(ctx context.Context, url string) (
+		contents map[string][]byte, err error)
+}
+
 func (c *CLI) OpenvpnConfig(logger OpenvpnConfigLogger, source sources.Source) error {
 	storage, err := storage.New(logger, constants.ServersData)
 	if err != nil {
@@ -38,7 +39,7 @@ func (c *CLI) OpenvpnConfig(logger OpenvpnConfigLogger, source sources.Source) e
 	}
 
 	// Unused by this CLI command
-	unzipper := (unzip.Unzipper)(nil)
+	unzipper := (Unzipper)(nil)
 	client := (*http.Client)(nil)
 	warner := (Warner)(nil)