* keep ./services for instances
./profiles is for config-only modules
./services are like profiles, but configure a single instance of a
service. Those are fronted by Nginx as the load-balancer and have a DNS
entry as well.
* ci: build build03 as well
* move hydra to services
* move matterbridge to services
* move marvin-mk2 to services
* build01: share the remainder profiles
* build02: use the nix-community-cache
* fixup kexec
* rename profiles to roles
* README: sync with reality
