r.useExtension(...)
Overview
Section titled “Overview”r.useExtension(extensionName, entity, options?) — opts an entity into a
registrar extension declared via r.extendsRegistrar: runs its
onRegister, merges its extra schema fields, and installs its entity
hooks at registry build time. The options bag is passed verbatim to
onRegister (per-entity configuration). Boot-validation throws when the
extension name does not exist.
From packages/framework/src/engine/feature-ast/patterns.ts -> UseExtensionPattern