NGINX Plus: support enforce_initial_report field

[tataruty]

Proposed changes

Problem:

As a potential NGINX Plus user,
I want to have a grace period for my initial licensing report,
So that I can validate NGF as a PoC without restriction.

NGF currently sets enforce_initial_report off; for NGINX Plus data planes when initially installing, but once the first configuration is sent from the control plane to the data plane, this directive is removed (defaulting to on). Users should be able to set this field themselves for other circumstances, like PoC testing or exemptions.

For reference: https://nginx.org/en/docs/ngx_mgmt_module.html#enforce_initial_report

Solution:
add a CLI argument to the controller to enable or disable the initial report enforcement
set the field in the nginx config based on the user input
the existing bootstrap config that sets this field to off should be left as-is to ensure startup succeeds
update the cli flag document
add helm chart flag to the existing nginx plus usage section

Testing:

• Added cli flag to unit test
• test helm installation:

1. install with command: make install-ngf-local-build-with-plus HELM_PARAMETERS="--set nginx.usage.enforceInitialReport=false"
   result:

2. Install with command: make install-ngf-local-build-with-plus HELM_PARAMETERS="--set nginx.usage.enforceInitialReport=true"
   result:

3. Install with command: make install-ngf-local-build-with-plus
   result:

Please focus on (optional):

Closes #3790

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

❌ Patch coverage is 95.94595% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.86%. Comparing base (84a517f) to head (dd95cfa).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/gateway/commands.go	95.65%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3899      +/-   ##
==========================================
+ Coverage   86.82%   86.86%   +0.04%     
==========================================
  Files         128      128              
  Lines       16503    16519      +16     
  Branches       62       62              
==========================================
+ Hits        14329    14350      +21     
+ Misses       1996     1990       -6     
- Partials      178      179       +1     

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[ciarams87]

Just one small comment, otherwise looks good!

[sjberman]

Nice work!