Standardise a mailer setup

At least on Debian 10, use msmtp and install a basic configuration.
Previously the network was using a mishmash of exim, sendmail or
whatever happened to be installed. For the moment, install the config
also on debian9, some of which are using ssmtp, which is no longer
maintained in debian :(

modules/rhizo_base/manifests/init.pp

@@ -681,4 +681,14 @@ schedule { 'never':
       ip => '10.23.0.11',
   }
 
+  file { '/etc/aliases':
+        ensure => 'present',
+        source => 'puppet:///modules/rhizo_base/etc/aliases'
+  }
+
+  file { '/etc/msmtprc':
+        ensure => 'present',
+        content => template('rhizo_base/msmtprc.erb')
+  }
+
 }

modules/rhizo_base/manifests/packages.pp

@@ -38,7 +38,7 @@ class rhizo_base::packages::common {
 
 class rhizo_base::packages::buster inherits rhizo_base::packages::common {
 
-  package { ['libcdk5nc6' ]:
+  package { ['libcdk5nc6', 'msmtp-mta' ]:
       ensure  => installed,
       require => Class['rhizo_base::apt'],
     }