Add Documentation on how to use and configure AuthenticationFilter for BasicAuth

[shaun-nx]

Overview

As a user of NGF
I would like there to be an document on how to use and configure the AuthenticaitonFilter
So that I can have a point of reference on how to configure and troubleshoot this resource

Acceptance

• Add new document for AuthenticationFilter to our NGF public docs
• Documentation should include how to setup and configure the resource for Basic Auth only
• Added to the "Traffic Security" section of the docs