Adds `/api-docs/openapi.json` and `/rapidoc` endpoints to both
kumod and tsa-daemon.
The former exposes the subset of the API that is expressable
in the openapi schema as a json file that can be imported into
other tools.
The latter is a single-page web app that consumes the former
to provide an interactive API explorer.
We're using rapidoc for this, because I happen to think it looks
nicest and easiest to use, and we can integrate it into the docs
fairly nicely.
Which leads in nicely to say: I've integrated a read-only version
of rapidoc into the docs, and it even detects and adjusts to the
selected light/dark mode.
The `docs/update-openapi.sh` extracts the openapi.json data from
kumod and tsa-daemon and outputs to the correct place in the docs
directory structure to enable this.
refs: https://github.com/KumoCorp/kumomta/issues/96
Wez Furlong