It's called OpenOTP, and it's a MacOS application I made that autofills your email verification codes into whatever website you're trying to log into. It took me about a week from start to finish!
You can take a look at how it works and how to install it at https://openotp.app . Unfortunately the software is not signed, as I don't have a dev license :(. To avoid this, you can also use the one-liner 'curl -fsSL https://openotp.app/install.sh | sh'
I'd love if you could take a look at it and let me know what you think! Cheers :)