Fix #1217: Support PINs for security keys

[jumde]

fix #1217

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• My patch or PR title has a standard commit message that looks like Fix #123: This fixes the shattered coffee cup! (or No Bug: <message> if no relevant ticket)
• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New files have MPL-2.0 license header.

Test Plan:

1. Set a PIN on your YubiKey using Yubikey Manager
2. Navigate to demo.yubico.com/u2f/
3. Confirm that a PIN is prompted during the registration workflow.
4. Entering a correct PIN should successfully complete registration
5. Entering an incorrect PIN should throw an error.

Screenshots:

Reviewer Checklist:

• PR is linked to an issue via Zenhub.
• Issues are assigned to at least one epic.
• Issues include necessary QA labels:
  • QA/(Yes|No)
  • release-notes/(include|exclude)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable)

[jumde]

Added a small change for exclude credentials: 949394d

@Brandon-T Exclude Credentials is optional for the registration request, so using an Optional type. Let me know if you have any concerns.