By looking up the docs we can find that the magic combo is admin as username and admin as password.
However if you changed some configuration file you should be able to find it there.
The default config file can be found here: $WORKING_DIR/conf/defaults.ini and can be overridden using the --config parameter
The item in the config you’re looking for should be in the section:
[security]
admin_user = admin
admin_password = admin