CLPR: Core Middleware APIs

This issue is a place holder for the development of the core middleware APIs and defining a minimal barebones exercise of the APIs as System Contracts, following the core practice of other System Contracts.

This is a placeholder for core middleware APIs and a minimal barebones exercise as System Contracts; no files, tests, or entry points are named. Start by reviewing the existing System Contracts and defining the API scope. Done means the core APIs and their minimal exercise are specified and implemented.

Written by the indexing model from the issue text.