Add unit tests for GetVersion

[3vilhamster]

What changed?
Add unit tests for GetVersion and added a log for error in UpsertSearchAttributes.

The error handling is a noop and happens only if we cannot serialize data. This is not expected to happen with the existing GetVersion API.

Why?
Improving test coverage.

How did you test it?

Potential risks

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 80.63%. Comparing base (17b9b1a) to head (3271d90).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/internal_event_handlers.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
internal/internal_event_handlers.go	62.03% <25.00%> (+2.91%)	⬆️

... and 1 file with indirect coverage changes

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