Add prestashop Order field

I am trying to make an order commenting module myself. All i need to do is just to create message field in payment step process or in any of other steps(doesn't matter) and show it in admin panel. Already set up the module. Overrided class Order. Added in constructor:

<?php

class Order extends OrderCore
{
    public function __construct($id = null, $id_lang = null)
    {
        self::$definition['fields']['message'] = [
            'type' => self::TYPE_STRING,
            'required' => false
        ];
        parent::__construct($id, $id_lang);
    }
}

Created template file and injected into hookDisplayPaymentTop:

<div class="form-group">
    <label for="comment">Leave comment about order:</label>
    <textarea class="form-control" name="message"  rows="5" id="comment"></textarea>
</div>

But i don't know what controller&function is responsible to handle submit to actually fill the field.

Help me please

Solution

In a native prestashop, during the order process you already have a field that allows the customer to leave a comment on his order.

It is not necessary to modify anything for that.

Regards,