Storage client

Storage clients contain information about how to retrieve an individual entity as well as to retrieve a list of entities. The list of items is used for entity browsing. The individual entities can be reached with /external_entity_machine_name/id  This route works independent of the list, that means that also items outside the list can be reached

Each storage client plugin can provide its own configuration. Storage clients can  provide a specific implementation for count queries. Storage clients  have the possibility to load multiple items at once. For example: loading 50 items will not require 50 separate requests to be sent, instead 1 will do (if the external source supports this of course).  Custom storage client plugins should be put in src/Plugin/ExternalEntities/StorageClient.