Companion

Writes the caller itself as the development identity headers (DevelopmentHeaders.of), which a host reads in a development profile alone, with no identity provider. For a test or a service tried out on one machine (a test server's typed clients); a deployment's peer never reads them.

Forwards the headers of the request being served, as the host puts them in the coroutine context (ForwardedHeaders); none outside such a request.

Forwards nothing: the peer serves the call as an anonymous caller, if it lets one.