refactor: add custom Exception class

src/Exception/MalformedDomainException.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Exception;
+
+class MalformedDomainException extends \Exception
+{
+    public static function fromDomain(string $ldhName): MalformedDomainException
+    {
+        return new MalformedDomainException("Domain name ($ldhName) must contain at least one dot");
+    }
+}