How to protect GitLab-connected SSH key with Yubikey

This post details the integration of FIDO/U2F hardware security keys (YubiKeys) for SSH key authentication, enabling two-factor authentication for Git operations via SSH. It covers generating `ecdsa-sk` and `ed25519-sk` key types, updating OpenSSH to version 8.2+, and adding the public key to GitLab's SSH settings. It also highlights the use of resident keys for easier sharing across devices.