chore: introduce additional unit tests for api packages

[odubajDT]

This PR

• refactor api packages
• cover api packages by unit tests
• adapt changes

Related Issues

Fixes #394

[codecov]

Codecov Report

Merging #420 (0d71726) into main (4290978) will increase coverage by 28.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             main     #420       +/-   ##
===========================================
+ Coverage   56.24%   84.26%   +28.01%     
===========================================
  Files          12       19        +7     
  Lines         857     1061      +204     
===========================================
+ Hits          482      894      +412     
+ Misses        356      138      -218     
- Partials       19       29       +10     

Impacted Files	Coverage Δ
...is/core/v1alpha2/featureflagconfiguration_types.go	50.00% <ø> (+33.33%)	⬆️
...is/core/v1alpha1/featureflagconfiguration_types.go	100.00% <100.00%> (ø)
...pis/core/v1alpha1/flagsourceconfiguration_types.go	100.00% <100.00%> (ø)
...ollers/core/featureflagconfiguration/controller.go	54.63% <100.00%> (ø)
pkg/utils/utils.go	100.00% <100.00%> (ø)
webhooks/pod_webhook.go	89.22% <100.00%> (+46.11%)	⬆️

... and 6 files with indirect coverage changes

Flag	Coverage Δ
component-tests	84.86% <100.00%> (?)
unit-tests	64.46% <87.50%> (+8.22%)	⬆️

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[toddbaert]

lgtm