Add controller class for Group-level Protected Environments

What does this MR do and why?

This MR is a vertical slice for Group-level UI for Protected Environment settings feature. It adds the following changes:

• Add controller class for Group-level Protected Environments
• Add a feature flag group_level_protected_environment. This flag won't be enabled until all vertical split has been merged.

Screenshots or screen recordings

You can see the walk-through video for the full details, or the PoC MR about the prospect code changes to complete the feature.

How to set up and validate locally

You can see the walk-through video for the full details, or the PoC MR about the prospect code changes to complete the feature.

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.