feat: can validate fido-u2f attestation

[grzuy]

To do:

• fix rubocop
• rename x and y
• memoize when necessary
• fix merge conflicts

[brauliomartinezlm]

I reviewed changes. Looks pretty awesome 🍺 .
Only comments were about x and y methods, but saw them in your checklist.

I also wondered around for a while around how to make AuthenticatorData handle data structure a bit niftier but couldn't quickly come up with something better to avoid the constant usage to name lengths and positions.

[grzuy]

Haha, yes. AuthenticatorData a bit tricky. Something to keep in mind for the future, if we find a better way to handle that.