Implement dereferencing of HCA metadata in Ingest Core or separate Schema Service

[aaclan-ebi]

Currently we maintain different schema endpoints in Ingest Core

https://api.ingest.archive.data.humancellatlas.org/schemas/search/

However, there's a recent requirement to support retrieving dereferenced schema to be used internally by the Ingest UI to generate the forms automatically. This has been implemented in the Ingest Broker for convenience at the moment. ebi-ait/ingest-broker#9

We want to either support all schema-related functionalities in one place either in Core or a Separate Schema service.