Post-Install Script to Simplify Install for Helper Users

[MHillyer]

As a new user there is a lot to do before I reach a full install. The sample config is working but very basic, and the example config in the documentation requires a lot of placement of supporting TOML files to get a working server.

Introduce a post-install script similar to MySQL that asks a few basic questions and assembles a functioning configuration.

This script could ask for a first sending domain and relay hosts and use the answers to put together a functioning configuration based on the example script, with the basics of IPs, relay domains, relay hosts, DKIM signing, etc.