Automatically include mod_expires if required via vhost directories

[ekohl]

Summary

Similar to other options passed in the vhost's directory this now inspects the directories entry and if expires_* is passed, mod_expires` is included.

Additional Context

This is a pattern that I've started to apply more and more. It allows passing complex directories (also via Hiera). On our servers we disable the default mods and this ensures we have the correct mods enabled.

Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [ ] Manually verified. (For example puppet apply)