Add additional unit tests

[omarfawzi]

Summary

• add tests for HTTPResponseError methods
• test HTTP client version parsing
• test router provider helpers
• test gRPC helper utilities

Testing

• go test ./... -coverprofile=coverage.out
• go tool cover -func=coverage.out | tail -n 1

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https://chatgpt.com/codex/tasks/task_e_684bd7ecf8cc8323ba46faaebce27121

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 34.66%. Comparing base (79a3d3c) to head (562268f).
Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master       #6       +/-   ##
===========================================
+ Coverage   18.07%   34.66%   +16.58%     
===========================================
  Files          19       19               
  Lines         603      603               
===========================================
+ Hits          109      209      +100     
+ Misses        491      385      -106     
- Partials        3        9        +6     

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