This does two things:
- add a group "mumblecert" which is allowed to read the mumble.hacc.space
cert, and add both nginx and murmur's users to it
- remove the website's derivation from services/murmur.nix and instead
add it to the websites/ dir and handle it the same as all our other sites
however, for some reason, ACME still fails. Hopefully it's just the
rate limit, but it does look suspicious; there' still a
"www.muc.hacc.space" in the log that oughtn't be there …
idea is to have a directory `websites/` which contains all our static
sites, with the name of each subdirectory also being their domain. Then
Nix can just read that directory during build-time and automatically
generate nginx virtualHosts for all of them (note that the
subdirectories have to contain a `default.nix` specifying how to build
the site for that to work).
Thus we could avoid the dependency on gitlab pages.
