chore(constants): remove and move constant paths

- Remove unused paths
- Move paths to inline constants if used only once

internal/cli/clientkey.go

@@ -7,7 +7,7 @@ import (
 	"os"
 	"strings"
 
-	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/configuration/sources/files"
 )
 
 type ClientKeyFormatter interface {
@@ -16,7 +16,7 @@ type ClientKeyFormatter interface {
 
 func (c *CLI) ClientKey(args []string) error {
 	flagSet := flag.NewFlagSet("clientkey", flag.ExitOnError)
-	filepath := flagSet.String("path", constants.ClientKey, "file path to the client.key file")
+	filepath := flagSet.String("path", files.OpenVPNClientKeyPath, "file path to the client.key file")
 	if err := flagSet.Parse(args); err != nil {
 		return err
 	}