If the manisfests of a ABI cluster contain an invalid hostname the installer is able to create the image but later the installation will not start for `forbidden hostname` the allowed pattern is `^[a-z0-9][a-z0-9-]{0,62}(?:[.][a-z0-9-]{1,63})*$`

seen in 4.19 and 4.18

always

    1. Prepare install-config.yaml and agent-config.yaml with invalid hostname, for example with capital letters. 
    2. Create the ISO and confirm no errors or warning shown.
    3. Start the installation and verify it stuck on validating the hosts.
    

Image is created but installation will not start causing time to troubleshoot something that can be prevented from the beginning.

The installer should fail in advance.