Interface for actors registries.
lookupActor(handle [, creds])
Name Type Argument Description
string Actor handle from the authenticator.
Registry-specific actor credentials, if any.
Returns:Actor record or a promise of it. Returning
nullor a promise that resolves to a
nullmeans the actor does not exist for the handle. If
credsis provided, may also mean that the credentials are invalid. If a promise is returned and the promise is rejected, it indicates an unexpected internal error.