feat: implement download

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

lib/Client/ClientInterface.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace KTXM\ProviderImap\Client;
 
 use KTXM\ProviderImap\Client\Command\CommandInterface;
+use KTXM\ProviderImap\Client\FetchTarget;
 
 interface ClientInterface
 {
@@ -21,4 +22,11 @@ interface ClientInterface
      * @return TResult
      */
     public function perform(CommandInterface $command): mixed;
+
+    /**
+     * Stream the raw bytes of a single IMAP BODY section without buffering.
+     *
+     * @return \Generator<string>  raw (transfer-encoded) bytes from the socket
+     */
+    public function download(FetchTarget $target, string $section, int $chunkSize = 8192): \Generator;
 }