Previously, some files were copied into the Nixpkgs tree, which meant
we wouldn't easily be able to update them, and was also just messy.
The reason it was done that way before was so that a few NixOS
options could be substituted in. Some problems with doing it this way
were that the _package_ changed depending on the values of the
settings, which is pretty strange, and also that it only allowed those
few settings to be set.
In the new model, mailman-web is a usable package without needing to
override, and I've implemented the NixOS options in a much more
flexible way. NixOS' mailman-web config file first reads the
mailman-web settings to use as defaults, but then it loads another
configuration file generated from the new services.mailman.webSettings
option, so _any_ mailman-web Django setting can be customised by the
user, rather than just the three that were supported before. I've
kept the old options, but there might not really be any good reason to
keep them.
We already had python3Packages.mailman, but that's only really usable
as a library. The only other option was to create a whole Python
environment, which was undesirable to install as a system-wide
package.
It's likely that a user might want to set multiple values for
relay_domains, transport_maps, and local_recipient_maps, and the order
is significant. This means that there's no good way to set these
across multiple NixOS modules, and they should probably all be set
together in the user's Postfix configuration.
So, rather than setting these in the Mailman module, just make the
Mailman module check that the values it needs to occur somewhere, and
advise the user on what to set if not.
This replaces all Mailman secrets with ones that are generated the
first time the service is run. This replaces the hyperkittyApiKey
option, which would lead to a secret in the world-readable store.
Even worse were the secrets hard-coded into mailman-web, which are not
just world-readable, but identical for all users!
services.mailman.hyperkittyApiKey has been removed, and so can no
longer be used to determine whether to enable Hyperkitty. In its
place, there is a new option, services.mailman.hyperkitty.enable. For
consistency, services.mailman.hyperkittyBaseUrl has been renamed to
services.mailman.hyperkitty.baseUrl.
