How to add custom site config to silverstipe?

I am working on building a module with silverstripe and I wanted to store some custom config for my module in the db. I went through the documentation and this is what I am trying:

By looking at silverstripe documentation:

<?php
namespace Poptin\Silverstripe;

use SilverStripe\Forms\FieldList;
use SilverStripe\Forms\HTMLEditor\HTMLEditorField;
use SilverStripe\ORM\DataExtension;

class PoptinSiteConfig extends DataExtension 
{
    
    private static $db = [
        'FooterContent' => 'HTMLText'
    ];

    public function updateCMSFields(FieldList $fields) 
    {
        $fields->addFieldToTab("Root.Main", 
            new HTMLEditorField("FooterContent", "Footer Content")
        );
    }
}

And in the config file:

Silverstripe\SiteConfig\SiteConfig:
    extensions:
        - \Poptin\SilverStripe\PoptinSiteConfig

But I am not sure what this will do when I run /dev/build/?flush. Will it create a new table for my site config, if yes, is it going to have just one field called FooterContent? I am not sure, where can I read more about this in the docs to understand this before I run it, in case it makes changes to my database, would like to be sure.

Solution

DataExtensions add columns to the existing table (fyi, subclasses create new tables but this isn't applicable here).

With Silverstripe you don't have to think too much about the database; it's managed for you via the ORM.