Add database management API server

[hello-smile6]

This should be good enough for an initial implementation. Post-merge requirements:

• create local service user on Nest and corresponding Postgres superuser account
• Write systemd service to auto-start webserver

TODO: modify nest CLI to call this API when creating a database instead of invoking a shell script, and potentially modify nest bot to call /setup when a new user is created rather than setting up databases in a shell script

[hello-smile6]

Is merging okay?

[polypixeldev]

yeah, merge when you're ready!