chore: avoid duplication in connected accounts error handling

[frederikprijck]

This PR tries to improve readability by moving connected account related error handling into a separate function.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 69.04762% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.37%. Comparing base (05ec221) to head (030daa2).

Files with missing lines	Patch %	Lines
src/server/auth-client.ts	69.04%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2404      +/-   ##
==========================================
+ Coverage   87.90%   88.37%   +0.46%     
==========================================
  Files          37       37              
  Lines        4127     4119       -8     
  Branches      818      820       +2     
==========================================
+ Hits         3628     3640      +12     
+ Misses        496      476      -20     
  Partials        3        3              

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