How to configure custom hiera for foreman-installer to keep custom Postgres tuning

Issue

I am working on a custom hiera to ensure performance tuning changes are not overwritten when Satellite 6 is updated/upgraded. I've been able to determine the proper settings for pulp and foreman, but I'm having difficulty determining the proper entries to use for tuning PostgreSQL.

If I'm reading the config_entry.pp manifest, I would need to add the following to my custom hiera:

postgresql::server::config_entry:PARAMETER: VALUE

However, many of the parameters I want to change appear not to be supported by the module. It looks like I could set:

postgresql::server::config_entry:max_connections: 500
postgresql::server::config_entry:shared_buffers: 7680MB
postgresql::server::config_entry:wal_buffers: 16MB

However, it doesn't appear I can change the following parameters:

maintenance_work_mem
checkpoint_completion_target
checkpoint_segments
work_mem

So, I have a couple of questions:

1) Is the format I have listed correct for the custom hiera for the supported parameters?
2) For those parameters not supported by the module, does the installer overwrite the entire postgresql.conf file, or edit the file to modify the parameters to the values specified -- in other words, can I customize the file for parameters not supported by the module and have those values remain unchanged after an upgrade?