Adding a Schema to LDAP

I’ve had an LDAP setup for a quite a while1, but I’ve never really used it. Sure, I could set up my Dokuwiki to get the logins and groups from LDAP and that’s kind of what it’s for, but that wasn’t enough. I wanted to use LDAP as a central configuration/setup/inventory management system. Configure my mail server to lookup email addresses there, assign port numbers and hosts for my services from there, etc.