backstage/.changeset/metal-garlics-fetch.md

@backstage/frontend-plugin-api, @backstage/frontend-app-api

@backstage/frontend-plugin-api	@backstage/frontend-app-api
patch	patch

Moved several implementations of built-in APIs from being hardcoded in the app to instead be provided as API extensions. This moves all API-related inputs from the app extension to the respective API extensions. For example, extensions created with ThemeBlueprint are now attached to the themes input of api:app-theme rather than the app extension.