postfix-ldap required for ldap lookup type on RHEL8+

[edrude]

Pull Request (PR) description

Install postfix-ldap package when ldap=true on RHEL8+

This Pull Request (PR) fixes the following issues

Fixes #397

[kenyon]

Wouldn't it be better to use the module's hiera data for this kind of thing rather than using conditionals in code?

[smortex]

Wouldn't it be better to use the module's hiera data for this kind of thing rather than using conditionals in code?

+1: some Array[String[1]] $ldap_packages parameter with the right default values in hiera and a package { $postfix::ldap_packages: ensure => installed } in the manifest seems more flexible.

[edrude]

Absolutely, I was just trying to get something down. If I get some time tomorrow I will update it.

[edrude]

Made the suggested changes.

One thing I have been struggling with when using this module. I find a few options that would appear at first to be useful for me, but end up being too opinionated. $mta and $ldap are both examples.

In the case of $ldap I want my ldap lookups to be a part of 'virtual_alias_maps' instead of 'alias_maps', but if $ldap = true the ldap config file is added to the 'alias_maps' option.

I also can't use $mta because if $mta = true then 'virtual_alias_maps' is set for me.

I see the merit of building in some common opinionated scenarios, maybe this is more of a documentation issue. If the docs had some callout to "these options are equivalent to" or "opinionated setup of" I think I would have arrived where I am now much faster.

Specifically for $ldap it may make sense to separate out the installation of the $ldap_packages so that you can still "enable ldap" without doing everything that setting $ldap to true does. Anything that separates out "making postfix ready to use ldap" from "configuring how postfix uses ldap"

[smortex]

One thing I have been struggling with when using this module. I find a few options that would appear at first to be useful for me, but end up being too opinionated. $mta and $ldap are both examples.

I quite agree. On one hand some interfaces are really not great IMHO, but on the other hand we don't want to break the setup of users of the module. It is hard to change things when they are done in a certain way. That being said, I think that all efforts to make diving in with the module are good to have. Feel free to send PRs.