fix: use admission webhook namespace if pod namespace is empty

[L3o-pold]

This PR

Fix issue with admission webhook on older k8s version

Related Issues

Fixes #500

Notes

Follow-up Tasks

We then can say open-feature-operator is working on k8s >= 1.22

How to test

I tested on kind with a 1.22 image (image: kindest/node:v1.22.9) .

kind create cluster --config ./test/e2e/kind-cluster.yml
kind load docker-image local-image-tag:latest
IMG=local-image-tag:latest make deploy-operator
IMG=local-image-tag:latest make e2e-test

[codecov]

Codecov Report

Merging #503 (94983d4) into main (1620a08) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #503      +/-   ##
==========================================
+ Coverage   82.62%   82.67%   +0.04%     
==========================================
  Files          22       22              
  Lines        1393     1397       +4     
==========================================
+ Hits         1151     1155       +4     
  Misses        205      205              
  Partials       37       37              

Files Changed	Coverage Δ
webhooks/pod_webhook.go	89.63% <100.00%> (+0.25%)	⬆️

Flag	Coverage Δ
unit-tests	82.67% <100.00%> (+0.04%)	⬆️

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[L3o-pold]

d234410 reverted this PR...

[beeme1mr]

Hi @L3o-pold, sorry about that! We've reintroduced this feature in v0.5.1 and expanded our test coverage to ensure it isn't accidentally removed again.