Autoconfig can lead to invalid netplan

[x13-me]

Autoconfig documentation needs updating to clarify what changes it makes to the netplan, it is entirely possible to generate an invalid netplan

[x13-me]

if PRESET_NET_CHANGE_DEFAULTS="1" and PRESET_NET_ETHERNET_ENABLED="1", but a static IP is not provided, the netplan config generated will work at first boot, then break and prevent networking after a reboot

Documentation should be updated to reflect this

[igorpecovnik]

but a static IP is not provided

Perhaps adding IF this is not provided, to display WARNING and skip auto-config due to this?