Using sane defaults

[onlime]

@jobcespedes What a wonderful Ansible role with great code quality! Thanks a lot. It helped me a lot getting Mailman 3 up and running.

I struggled a bit with your defaults, especially since it was hard to change the default mailman-web (Postorius) admin user's email root@localhost afterwards, if that was forgotten to getting overwritten on deploy.

Here's my changes:

• Renamed mailman3_service_name var to mailman3_server_name which makes more sense
• Bugfix: renamed mailman3_postfix_debconf_status to mailman3_debconf_status
• Using mailman-admin@YOURDOMAIN instead of changeme@YOURDOMAIN, since most tutorials recommend that
• Adding $alias_maps to Postfix local_recipient_maps, so that we could use an alias e.g. for postorius mailman-admin@YOURDOMAIN
• mailman-web: make DEFAULT_FROM_EMAIL and SERVER_EMAIL configurable
• mailman-web: enable django.contrib.admin in INSTALLED_APPS by default, as a Mailman 3 install without admin probably doesn't make much sense (and in my case errored out)
• mailman-web: disabled socialaccounts by also disabling django_mailman3.lib.auth.fedora (which probably nobody ever wants)
• introduce new mailman3_configure_postfix var to be able to only configure Postfix without installing it (for those who already use their own role to install Postfix)

Hope you can merge this. It was tested on a fresh Debian Bullseye 11.5 install.

Cheers, Philip