Unit tests for activity task handler

[3vilhamster]

Detailed Description
To improve test coverage, I've moved existing components to separate files and added unit tests for the activity handler.

Impact Analysis

• Backward Compatibility: Full
• Forward Compatibility: Full

Testing Plan

• Unit Tests: Unit tests and existing integration tests test
• Persistence Tests: unrelated
• Integration Tests: This could be verified with existing unit/integration tests and on canary deployment.
• Compatibility Tests: Unrelated

Rollout Plan

• What is the rollout plan? Simple rollout starting with canary
• Does the order of deployment matter? No
• Is it safe to rollback? Does the order of rollback matter? Yes
• Is there a kill switch to mitigate the impact immediately? Rollback

[codecov]

Codecov Report

Attention: Patch coverage is 97.38562% with 4 lines in your changes missing coverage. Please review.

Project coverage is 77.92%. Comparing base (a71b70f) to head (cf98af2).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/activity_task_handler.go	96.77%	3 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
internal/activity.go	89.71% <ø> (ø)
internal/auto_heartbeater.go	100.00% <100.00%> (ø)
internal/internal_task_handlers.go	81.61% <ø> (+0.17%)	⬆️
internal/activity_task_handler.go	96.77% <96.77%> (ø)

... and 2 files with indirect coverage changes

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[taylanisikdemir]

why not use table test to have less redundancy? this approach is hard to maintain especially while the function under test changes. requires changing N test bodies instead of 1

[3vilhamster]

I'm not sure if I can save much with table tests.
I think a setup will have many customizations and be hard to read.