POE2 Steam Upgrade

As the title says, I bought the basic package for early access on steam, and now I want to upgrade to the King of the Faridun Supporter Pack, I saw that I have the option to buy it from the game, paying the difference of 70 euros, my question is, this will the purchase be accompanied by a cd key to be added to steam as DLC?

Can anyone help me with this information? I want to make the purchase today.
I use Steam the most, and it's my passion, that's why I am so desperately want to know if I have a chance to add it to Steam as DLC.