docs: use Config\Auth::$tables

Author: kenjis

docs/customization/adding_attributes_to_users.md

@@ -19,24 +19,39 @@ And write code to add/drop columns.
 
 namespace App\Database\Migrations;
 
+use CodeIgniter\Database\Forge;
 use CodeIgniter\Database\Migration;
 
 class AddMobileNumberToUsers extends Migration
 {
+    /**
+     * @var string[]
+     */
+    private array $tables;
+
+    public function __construct(?Forge $forge = null)
+    {
+        parent::__construct($forge);
+
+        /** @var \Config\Auth $authConfig */
+        $authConfig   = config('Auth');
+        $this->tables = $authConfig->tables;
+    }
+
     public function up()
     {
         $fields = [
             'mobile_number' => ['type' => 'VARCHAR', 'constraint' => '20', 'null' => true],
         ];
-        $this->forge->addColumn('users', $fields);
+        $this->forge->addColumn($this->tables['users'], $fields);
     }
 
     public function down()
     {
         $fields = [
             'mobile_number',
         ];
-        $this->forge->dropColumn('users', $fields);
+        $this->forge->dropColumn($this->tables['users'], $fields);
     }
 }
 ```