pimcore/studio-backend-bundle ? reverse-engineered prompt

Build me the Studio Backend for Pimcore, as a backend bundle that acts as the main API layer for the admin side of the app.

I want it to expose a clean, documented API for working with assets, data objects, and documents, with a Swagger style docs page in dev and a JSON spec endpoint too. It should support real time updates, background work through Pimcore’s execution engine, and the generic data index and Mercure setup that Pimcore expects.

Please make it easy to extend with custom endpoints, filters, grid columns, document types, perspectives, widgets, and event hooks. The grid views should be configurable, with columns, filters, and data transformation support. It should also include GDPR data extraction support.

Use the existing Pimcore 12 bundle structure, keep the API descriptions translatable, and follow the repo’s docs where they help. If you need current library details, look them up online first.