Add PROXY-protocol listener support to slapd

[dabelenda]

Pull Request (PR) description

Since openldap 2.5 it is possible for slapd to use PROXY protocol listeners. This allows to get IPs of the clients through a load-balancer for logging and filtering purposes.

This PR add parameters to openldap::server to enable the usage of this feature.

This Pull Request (PR) fixes the following issues

N/A

[dabelenda]

The failures on Alma/Rock 8 and Debian 11 are expected, they install openldap 2.4 which does not support the feature...
I don't know how to either skip this test on these OSes or tell the test framework the failures are expected...

[dabelenda]

@bastelfreak any idea on how I can ignore the OSes that will fail due to an old version of openldap?

I can comment out the tests, too, but I don't think this is a good idea.

[bastelfreak]

I'm not sure what the best behaviour is. Should the module allow you to set the parameter, even on an unsuported OS? I think it would be better if the module would raise a proper error in that case.

[dabelenda]

Well, the default installation of openldap-server on these OSes does not support the parameter, but there are other packages for openldap that exist for these OSes (at least for RHEL8 I know an enterprise-supported openldap distribution), so hardcoding a failure in the manifest is weird and checking for the version of openldap is hard.