Federated Properties proof of concept has served its purpose and will no longer be used.
Its logic (code) is no longer needed and should be removed from Wikibase source code repository to reduce the unnecessary complexity.

Incomplete list of logic that's no longer needed

• wikibase/federated-properties "library" in lib/packages
• no longer needed abstractions in wikibase/data-model and elsewhere (e.g. PropertyId as an interface)
• Federated Properties specific services and other logic in repo/includes/FederatedProperties and their usages
• \Wikibase\DataAccess\EntitySourceDefinitions::getApiSourceForEntityType and its usages
• no longer needed abstractions in Wikibase Repo, Lib and/or DataAccess that have been introduced to allow using both "standard" and Federated Properties specific services