Redeem Steam key to account with Steam OpenID like Humble Bundle

Humble Bundle has started requiring the user to sign in through Steam's OpenID authentication where it then redeems the Steam key on the user's account. I was unable to find any documentation on this

How to Redeem a Gifted Bundle or Game – Humble Bundle

Steam (service) - Wikipedia

Anyway to find Steam keys that are revealed but not redeemed? : r

Ubisoft Support - Early Supporters Are Not Eligible For Free Games

GitHub - fabiojwalter/wssnippet: Snippets for: Bricks, Mjolnir

Insanely clever Steam credential stealing scam using fake Sign in

I made a tool that automates extracting and redeeming ALL Steam

Free Game Redemption Instructions – Humble Bundle

Humble Bundle] Humble intergalactic Bundle: PWYW for Space Hulk

What are Steam CD Keys? – PC Games for Steam

Steam User Code

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How to Buy a Humble Bundle and Redeem It on Steam

Insanely clever Steam credential stealing scam using fake Sign in

Account got Hijacked - Please DON'T make my mistake!