Implement Self-hosted models contingency navigation

What does this MR do and why?

This MR implements solution 1 of the contingency plans as outlined in the figma below.

Figma

The page was originally going to to appear in the unified Duo page which is currently being built in parallel. The page won't be completed in time for the 17.5 release, hence why we've pivoted to the solution implemented in this MR.

What does this MR do?

• Connects the SelfHostedDuoConfiguration component added here
• Updates the admin navigation menu

See UX Issue for details

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Admin menu

Before	After

Self-hosted Models

Before	After

AI Feature Settings

Before	After

Screen recording Screen_Recording_2024-10-09_at_4.19.24_PM

How to set up and validate locally

Prequisites

You will need an active GitLab ultimate license.

1. Start GDK instance in self-managed mode:

GITLAB_SIMULATE_SAAS=0 && gdk start

2. In the rails console, enable Code Suggestions and the custom models experiment:

Feature.enable(:ai_custom_model)
Feature.enable(:custom_models_vue_app)
Feature.enable(:custom_models_feature_settings_vue_app)
ApplicationSetting.first.update(duo_features_enabled: true)

Test it!

1. Log in as an admin
2. Visit the page Admin Area > Self-hosted models
   
3. Self-hosted models tab
   • You should be able to add/edit/delete self-hosted models
4. AI feature settings tab
   • You should be able to update AI features

Related to #493581 (closed)