Support dewy's supervisor

Dewy's supervisor works this:

• instruct release to each dewy with hostname taken
• caching artifacts
• also provide library for existing api embed

I am very much looking forward to it.

caching artifacts

It would be nice to be able to specify external repositories by URL, etc. for artifacts, in addition to getting them directly from the supervisor.

also provide library for existing api embed

For me personally, as long as there is a protocol specification (Open API Spec, Protocol Buffers) that dewy can talk to, that is enough.

Thanks!