Bind a container ID to an Endpoint

_As an endpoint owner on a system that support shifter I want to be able to manually map a container ID to my workers so I can run functions that depend on that container_

The issue names endpoint owners, workers, container IDs, and Shifter support but provides no files, tests, or entry points. Start by locating the endpoint and worker implementation and how container-related configuration is handled. Clarify the expected API, persistence, and mapping behavior; done should allow an owner to bind a container ID to workers and run functions that depend on it.

Written by the indexing model from the issue text.