Review, restructure and rewrite documentation for getting started with NGINX Ingress Controller

[ADubhlaoich]

Proposed changes

This pull request represents a large collection of work to improve the NGINX Ingress Controller documentation by restructuring the layout of "onboarding" documentation, then digging deep into individual pages to address certain issues.

The scope of changes includes:

• Rewriting, removing or combining text (Including entire pages)
• Changing absolute URL links to relative references
• Fixing incorrect noun usage in regard to product names
• Adherence to NGINX style guides, including preposition use and heading style (Sentence case)
• Compartmentalising integration documentation to their own section (Removing noise from critical paths)
• Adding an includes section to enable content re-use for similarly designed products (e.g App Protect WAF & DoS)

The driving force behind these changes is to make the overall user experience for people engaging with NGINX Ingress Controller for the first time to have a smoother onboarding experience. There will be subsequent requests for the documentation following this idea.

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a29e0ff) 51.96% compared to head (68b409e) 51.99%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4620      +/-   ##
==========================================
+ Coverage   51.96%   51.99%   +0.02%     
==========================================
  Files          59       59              
  Lines       16960    16960              
==========================================
+ Hits         8814     8818       +4     
+ Misses       7849     7847       -2     
+ Partials      297      295       -2     

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[ADubhlaoich]

PR almost ready for full review - fixing some additional errant artifacts of git merging.

Looks as though some API versioning and the docs themselves under /configuration got mangled.

[ADubhlaoich]

Everything should be good now - also included a small bandaid "fix" for something I noticed in a security configuration file.

[shaun-nx]

Please ignore my blocking change. I made a comment about the wrong section of the document 🤦

[brianehlert]

Lets just make sure we don't block the docs team.
It should be possible for them to fully own this and us not be gates for merging.
I think that would be an excellent way of working for all of us.