Feature flag as server side resource

The classic feature flags available today are implemented as key‑values with a special prefix and content type, and the App Configuration server-side treats them the same as any other key‑values. Introducing feature flags as server‑side resources provides several advantages, including stronger protocol support through a formal REST API specification rather than client‑side schema, built‑in data validation and consistency enforcement, isolated permission control on feature flags, and reusable resources that can be shared across multiple feature flags. This new model lays the foundation for future feature flag capabilities in App Configuration and opens the door to many new opportunities.