Switch to another Puppet module to manage Postfix

https://gitlab.com/shared-puppet-modules-group/postfix is deprecated.

One option is to switch to https://github.com/camptocamp/puppet-postfix but quite some features are missing e.g.
https://gitlab.com/shared-puppet-modules-group/postfix/milestones/1.

Parent Task: #15500 (closed)

Related issues

Blocks #13284

Original created by @intrigeri on 15511 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information