Block creation of backups if it would put the server over it's limit

app/Exceptions/Service/Backup/TooManyBackupsException.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Pterodactyl\Exceptions\Service\Backup;
+
+use Pterodactyl\Exceptions\DisplayException;
+
+class TooManyBackupsException extends DisplayException
+{
+    /**
+     * TooManyBackupsException constructor.
+     *
+     * @param int $backupLimit
+     */
+    public function __construct(int $backupLimit)
+    {
+        parent::__construct(
+            sprintf('Cannot create a new backup, this server has reached its limit of %d backups.', $backupLimit)
+        );
+    }
+}