Conditional registration support

[Firehed]

This adds a new optional parameter to the credential registration verification procedure (WebAuthn 7.1) to account for conditional mediation.

Verify that the UP bit of the flags in authData is set, unless options.mediation is set to conditional.

Note that this is only in the draft spec, but it's likely to remain materially unchanged since this exact tooling was described at WWDC24. Still, I'm going to leave this undocumented for now (besides the actual method signature) in case anything changes before the next published version.

Fixes #83.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.36%. Comparing base (dc5e32a) to head (58d465a).

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #85      +/-   ##
============================================
+ Coverage     81.26%   81.36%   +0.10%     
- Complexity      307      308       +1     
============================================
  Files            33       33              
  Lines           982      982              
============================================
+ Hits            798      799       +1     
+ Misses          184      183       -1     

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