我的客户属性定义如下:
$customerSetup->addAttribute(Customer::ENTITY, "attr_code",  [
            "type"     => "varchar",
            "backend"  => "",
            "label"    => "Attribute Label",
            "input"    => "text",
            "source"   => "Magento\Eav\Model\Entity\Attribute\Source\Table",
            "visible"  => true,
            "required" => false,
            "default"  => "",
            "frontend" => "",
            "unique"   => false,
            "note"     => "",
            'system'   => 0,
            'user_defined' => true
]);我的问题是:如果设置user_defined为,该属性有什么区别false?在哪种情况下应该设置user_defined为true或false?