fix: enable defaulter and validator in portal webhook

[bjwswang]

What type of PR is this?

/kind bug

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #264

Special notes for your reviewer

This webhook acutually has no specific functionalities yet,but it does sometime in the future.

[bjwswang]

@Henry-Gao-2004 After this pr got merged, you can continue your work.

[codecov[bot]]

Codecov Report

Merging #265 (bae31e1) into main (ea4a1d7) will increase coverage by 0.02%. The diff coverage is 28.57%.

@@            Coverage Diff             @@
##             main     #265      +/-   ##
==========================================
+ Coverage   17.38%   17.40%   +0.02%     
==========================================
  Files          33       33              
  Lines        3268     3274       +6     
==========================================
+ Hits          568      570       +2     
- Misses       2667     2671       +4     
  Partials       33       33              

Files Changed	Coverage Δ
api/v1alpha1/portal_webhook.go	23.07% <28.57%> (+3.07%)	:arrow_up:

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[Henry-Gao-2004]

@Henry-Gao-2004 After this pr got merged, you can continue your work.

Thank you! Nice work!