Add a doc on model authentication

What does this merge request do and why?

Follow-up on #222.

Under "eval_setup" add a link on model configuration to a new markdown dedicated to documenting the supported models and how to configure them:

This MR adds the new markdown file dedicated to model authentication only.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• I've ran the affected pipeline(s) to validate that nothing is broken.
• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.