Write a guide on how to use ClientSettingsPolicy

[kate-osborn]

As a user of NGF
I want a guide on NGF's ClientSettingsPolicy to implement the use cases this policy enables
So that I can make us of the policy in my own NGF deployment.

Acceptance

• A general NGF policy reference doc is created to detail all of the fields of the ClientSettingsPolicy and statuses of any of our custom policies.
• A guide is created to explain what NGF's ClientSettingsPolicy is and how to achieve the use cases the policy enables.
  • The values used in the guide are the most common values / use cases to make copy / paste easier.
  • The guide includes examples of success and failure statuses for the policy.
  • A use case is included to cover how to fix 413s
• Ensure our troubleshooting guide includes how to fix 413s