increase the identifier max size in DB

We have a lot of identifiers with size>20 after 2019-04.

db/migrations/20201109223011_increase_identifier_length.php

+<?php
+
+use Phinx\Migration\AbstractMigration;
+
+class IncreaseIdentifierLength extends AbstractMigration
+{
+    public function change()
+    {
+        $this->adapter->execute("ALTER TABLE dons modify COLUMN identifier VARCHAR(255) NULL;");
+    }
+}