[Fix]: Let assignment of annotations to Pod without any existing ones

[nepomucen]

What does this change resolve?

• Fixes the following error:
  2024-12-18T11:36:46.057252474Z panic: assignment to entry in nil map
  which occurs when controller tries to set annotations to Pod without existing ones.

Open questions or TODOs before merging if any

[github-actions]

Go test coverage: 85.6% for commit 53da70e

View coverage for all packages

# Package Name                                                         | Coverage
+ github.com/NCCloud/metadata-reflector/internal/clients               |    88.1%
+ github.com/NCCloud/metadata-reflector/internal/common                |   100.0%
+ github.com/NCCloud/metadata-reflector/internal/controllers/reflector |    83.0%
+ github.com/NCCloud/metadata-reflector/internal/metrics               |   100.0%

[BonySmoke]

@nepomucen great, thank you, this looks awesome! I wonder if we need to add the same for setting labels. Theoretically, there will be no case when the pod doesn't have labels because we use them to actually get the pod but to keep things error-free, let's add the same logic here, wdyt?

[BonySmoke]

Besides, I realized we need a similar logic for removing annotations and labels.
Maybe you could also add the logic for checking if labels/annotations exist here and here and if they don't exist, simply return that the pod was not updated.
Thank you, again!

[nepomucen]

I agree with you about the extending the fix's logic to other functions as well.
It's done already, please review the changes again.

[BonySmoke]

Thank you! Could you please cover these changes with tests as well 🙏

[nepomucen]

Sure, will do ...

[nepomucen]

The tests are now added.

[BonySmoke]

LGTM 🚀