GrowthBook Custom Hooks API
Sandboxed JavaScript validation hooks that run when features, configs, or their revisions are saved or published. Throwing an Error blocks the save; `addWarning(msg)` raises a soft warning. Hooks are scoped by projects, or pinned to a single feature/config via `entityType`/`entityId`; a config-scoped hook also runs for every config inheriting from it (its whole descendant lineage). Scope can be retargeted on update (or cleared with nulls). Requires an enterprise plan; not available on GrowthBook Cloud.