Add NginxGateway functional test

[bjee19]

Proposed changes

Add a functional test for the NginxGateway resource.

Problem: We would like a functional test for the NginxGateway resource to ensure its working correctly.

Solution: Add the functional test.

Testing: Test works.

Closes #1808

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

None

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.21%. Comparing base (2544818) to head (da027f8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2486   +/-   ##
=======================================
  Coverage   89.21%   89.21%           
=======================================
  Files         100      100           
  Lines        7539     7539           
  Branches       50       50           
=======================================
  Hits         6726     6726           
  Misses        756      756           
  Partials       57       57           

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[bjee19]

Should I try to start on #2449 and add some better logging? But I'm not too sure what could be a good start / example.