refactor: unify quotes encoding

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

lib/Client/Protocol/Command/AppendCommand.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace KTXM\ProviderImap\Client\Protocol\Command;
 
+use KTXM\ProviderImap\Client\Protocol\StringEncoder;
 use KTXM\ProviderImap\Client\ImapException;
 use KTXM\ProviderImap\Client\Protocol\RequestFrame;
 use KTXM\ProviderImap\Client\Protocol\Response\ContinuationResponse;
@@ -57,7 +58,7 @@ final class AppendCommand implements CommandInterface
 
         return new RequestFrame(sprintf(
             'APPEND %s %s{%d}',
-            $this->quote($this->mailbox),
+            StringEncoder::quote($this->mailbox),
             $flagSegment,
             strlen($this->literal),
         ));
@@ -86,10 +87,6 @@ final class AppendCommand implements CommandInterface
         throw new ImapException('APPEND did not receive a tagged completion response.');
     }
 
-    private function quote(string $mailbox): string
-    {
-        return '"' . addcslashes($mailbox, "\\\"") . '"';
-    }
 
     private function parseAppendUid(string $text): ?int
     {