Create GraphQL egress endpoint

[bburns]

idea for future adapter architecture

ob: I am already evaluating (low priority) GQL in my app to replace REST API and MQTT. In Nest framework, it is very easy to get (at least barebone) GQL API, optionally with auth'n and auth'z, incl TypeScript, Fastify (instead of Express), Mercurius (instead of Apollo), validation, however, the programming style is much different from what Brian is used to.

bb: add REST and GraphQL endpoints to the adapter diagram

[tukusejssirs]

This issue somewhat overlaps with #214.