chore(auth): Move HandleWebUiSignInResponse logic to use case

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:

• Moves callback logic of handleWebUiSignInReponse from RealAWSAuthCognitoPlugin to a usecase
• Adds code coverage which previously did not exist for this logic.

How did you test these changes?

• Tests should pass

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Ensure commit message has the appropriate scope (e.g fix(storage): message, feat(auth): message, chore(all): message)

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

[codecov]

Codecov Report

❌ Patch coverage is 78.72340% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.48%. Comparing base (36f7590) to head (1efa1f0).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3241      +/-   ##
==========================================
+ Coverage   55.38%   55.48%   +0.10%     
==========================================
  Files        1077     1078       +1     
  Lines       31905    31911       +6     
  Branches     4756     4757       +1     
==========================================
+ Hits        17670    17706      +36     
+ Misses      12392    12360      -32     
- Partials     1843     1845       +2     

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