Global Search vertical navigation search helper

What does this MR do and why?

1/4 Provide JSON data for Vue frontend vertical navigation

• Search Page vertical navigation search helper
  • Search Page layout changes
    • Move filters into their own component
      • Search Page Vue vertical navigation

Screenshots or screen recordings

This is backend MR there is no visual change

How to set up and validate locally

1. Checkout this branch
2. In rails console enable a feature flag

   Feature.enable(:search_page_vertical_nav)

3. execute or render

   search_navigation_json

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #293740 (closed)