test(e2e): add e2e tests for certificate resource

[phm07]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 58.62069% with 24 lines in your changes missing coverage. Please review.

Project coverage is 69.76%. Comparing base (2798902) to head (8e080df).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
test/e2e/certificate_util.go	57.89%	16 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #945      +/-   ##
==========================================
+ Coverage   69.53%   69.76%   +0.23%     
==========================================
  Files         244      245       +1     
  Lines       10654    10711      +57     
==========================================
+ Hits         7408     7473      +65     
+ Misses       2574     2562      -12     
- Partials      672      676       +4     

Flag	Coverage Δ
e2e	45.58% <58.62%> (+1.71%)	⬆️
unit	63.48% <0.00%> (ø)

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