Print QR code for webauthn verification link

[segiddins]

What was the end-user or developer problem that led to this PR?

Accessing the webauthn verification link is difficult if you use your phone for your passkeys

What is your fix for the problem, implemented in this PR?

Use vendored rqrcode_code lib to generate a QR code for the link, which is printed out when the output is a tty

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

[ioquatix]

This is brilliant.

[deivid-rodriguez]

@segiddins I'm not sure I have the knowledge to review this, but I can try to get up to speed if needed. The vendoring looks fine to me, though!

One thing that immediately comes to mind though is, should the information before the QR code be updated to give a bit of context about the QR code? Maybe:

You have enabled multi-factor authentication. Please visit #{url_with_port} to authenticate via security device, or alternatively scan the QR code below. If you can't verify using WebAuthn but have OTP enabled, you can re-run the gem signin command with the --otp [your_code] option.

[segiddins]

That's a good idea!

[simi]

@segiddins any plan to update this PR?

[segiddins]

Yes, I will circle back here