Add Private Feature Flag

Overview

Adds a new private feature flag to Ghost. Private flags appear in Labs settings under the "Private features" tab, visible only when developer experiments are enabled.

Read and follow the canonical feature flag guide before adding a flag. The guide covers when a Labs flag is appropriate, safe gating across server and Admin, testing, and the cleanup lifecycle.

For Admin 7 milestone flags, also use the Admin 7 feature flags skill for naming and shared presentation guidance.

Steps

1. Add the flag to ghost/core/shared/labs.js
   • Add the flag name (camelCase string) to the PRIVATE_FEATURES array.