fix(auth) Add underlying cause to fetchAuthSession error

[tylerjroach]

• PR title and description conform to Pull Request guidelines.

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Documentation update required?

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• 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)

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 43.02%. Comparing base (30a288e) to head (98e2e36).
Report is 66 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2750      +/-   ##
==========================================
+ Coverage   43.00%   43.02%   +0.01%     
==========================================
  Files         905      905              
  Lines       29178    29179       +1     
  Branches     4152     4153       +1     
==========================================
+ Hits        12548    12553       +5     
+ Misses      15271    15268       -3     
+ Partials     1359     1358       -1