The discovery ISO generated by the Assisted Installer comes with a core user
that has its password login disabled (although SSH access using the provided
public key is still supported).
However, it can sometimes be useful (e.g. when SSH isn't working), to login to the machine directly (with physical or BMC access), using a password. This can be done using the console login prompt that is shown after the ISO boots up.
To allow that, the user must have a password set. In order to set a password, it's possible to use the following script which allows editing the discovery ISO's ignition file core user with a password
This script takes the path of the downloaded discovery ISO file as its first argument, prompts the user to enter a password, and creates a similarly named ISO file in the same folder as the original one but with password login enabled.