In dc0983d58937a064d74d96f311ca10a88569480b (#29642) the example database configuration file always sets a host. Using a host means PostgreSQL can't use ident auth which means you must set a password. By commenting it out, you can simplify the instructions to (on EL but similar on Debian):

sudo yum -y install postgresql-server
sudo postgresql-setup --initdb
sudo systemctl enable --now postgresql
sudo -u postgres createuser $USERNAME
sudo -u postgres createdb --owner=$USERNAME foreman

Otherwise you need to provide a username/password as well and possibly set that up.