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.

Steps

1. Add the flag to ghost/core/core/shared/labs.js

   • Add the flag name (camelCase string) to the PRIVATE_FEATURES array.

2. Add a UI toggle in apps/admin-x-settings/src/components/settings/advanced/labs/private-features.tsx

   • Add a new entry to the features array with title, description, and flag (must match the string in labs.js).

3. Run tests and update the config API snapshot

   • Unit: cd ghost/core && pnpm test:single test/unit/shared/labs.test.js
   • Update snapshot and run e2e: cd ghost/core && UPDATE_SNAPSHOTS=1 pnpm test:single test/e2e-api/admin/config.test.js
   • Review the diff of ghost/core/test/e2e-api/admin/__snapshots__/config.test.js.snap to confirm only your new flag was added.