We're not going to be able to use the mailman-generated postfix maps
anyway, but that functionality seems coupled with the LMTP receiver.

So let's just make sure we don't need to call 'postmap', at least.

Lists is already the public_endpoint for lurker.

We can't use mysqldump as that requires permissions on the target
instance, before that instance has had the chance to start up and
create those permissions, so it can't work in our setup.

Use the s6 branch for apache2-users

See merge request !154

Remove DKIM from the postfix-in -> postfix-out message flow

See merge request !153

This way we won't accidentally sign incoming untrusted messages,
regardless of their headers.

Fix usage of ip/i6 attributes in favor of "ips"

See merge request !152

It requires float!249 first.