- Configuration template.
- Render configuration template in entrypoint.
- Storage volumes.
- slapd volume for ldapi:/// connection.
- Execute the sogod instead of apache, not sure what I'm going to do
  with Apache.

Use the Cron jobs from the Debian packages.

Root privileges are needed for installaing packages.

Let's see if it builds.

- Don't set the hostname, the SSL terminating should have that hostname.
- The network isn't external (it will probably already be there but it
  should be created if it isn't).

Inspired by
https://michael-prokop.at/blog/2021/02/16/how-to-properly-use-3rd-party-debian-repository-signing-keys-with-apt/
and https://wiki.debian.org/DebianRepository/UseThirdParty. Also use the
newer deb822 sources format.

Installation, cron jobs, surrounding services. Missing configuration and
whatnot.

Also, run it in CI.