fix: Avoid conflicts on deck attachments folder name

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Service/ConfigService.php

@@ -230,4 +230,12 @@ class ConfigService {
 
 		return $this->config->getUserValue($userId ?? $this->getUserId(), 'deck', 'attachment_folder', '/Deck');
 	}
+
+	public function setAttachmentFolder(?string $userId = null, string $path): void {
+		if ($userId === null && $this->getUserId() === null) {
+			throw new NoPermissionException('Must be logged in get the attachment folder');
+		}
+
+		$this->config->setUserValue($userId ?? $this->getUserId(), 'deck', 'attachment_folder', $path);
+	}
 }