chore(build): add default init for ChallengeOptions

[thisisabhash]

Issue #, if available:
None

Description of changes:
Build fix for missing default initializer for challengeOptions

Check points: (check or cross out if not relevant)

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 28.86%. Comparing base (94194cb) to head (cabceaf).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #202   +/-   ##
=======================================
  Coverage   28.86%   28.86%           
=======================================
  Files          58       58           
  Lines        3104     3104           
=======================================
  Hits          896      896           
  Misses       2208     2208           

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