Feat: Pending Email Change Updates, Moving Mailables to core

src/Customer/Exceptions/EmailAlreadyTakenException.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Modules\Core\Customer\Exceptions;
+
+use RuntimeException;
+
+/**
+ * Thrown by Modules\Core\Customer\Services\CustomerEmailChangeService when
+ * the requested new email already belongs to a different user — checked
+ * both up front (request()) and again at confirm() time, since someone
+ * else could sign up with that address in the window between the two.
+ */
+class EmailAlreadyTakenException extends RuntimeException
+{
+    public function __construct()
+    {
+        parent::__construct('That email address is already in use.');
+    }
+}