Assembles config into a system-map which can be used with com.stuartsierra.component/start-system.

config - configuration for the system

component-ids - a sequence of component ids. When provided, only the necessary parts of the system map to support those components will be included in the final system map. By default, the returned system contains all components from the supplied config.

Applies any merge definitions, then optionally selects just the specified subset of components, including transitive dependencies.

This is useful for testing, to see the intermediate state before components are instantiated.