Various software on EDPM nodes expect an FQDN. We should require osdpns spec.nodes[].hostName to always become FQDN, and add a webhook validation that an FQDN is set there. The ask is exactly about prohibiting specifying shortnames completely in any possible osdpns inputs.

Background:

Floating shortnames / fullnames issues may be caused by different things (cloud-init and os-net-config conflicts or incomplete apply resulted in errors, missing domain definition in netconfig, dns issues, race conditions) but all result in a broken hypervisor configuration.

We shouldn't attempt to set an FQDN ourselves in the product if one isn't already set by the time we are running the ansible deployment. For preprovisioned, this means documenting the requirement, how to set one, and how to check one is set. For provisioned, an FQDN should be set automatically during baremetal provisioning (needs to be checked, I'm not sure of the current behavior).

There is also already a validation in the edpm-ansible role edpm_nodes_validation, but it's disabled by default due to edpm_nodes_validation_validate_fqdn defaulting to false. The validation also checks that the FQDN is in /etc/hosts, which is not necessarily required or always true (unless we document that and start making it true). I think the correct way to set the FQDN is likely with hostnamectl which should populate /etc/hostname. We likely should use hostnamectl and/or /etc/hostname in a new validation.