What is the best practice to update nginx advagg settings for an aegir install?

Problem/Motivation

What is the best practice to update Nginx Advagg settings for an Aegir install?

Some settings exist but need to be updated here: /var/aegir/config/includes/nginx_vhost_common.conf

I want to update them as seen here:
https://www.drupal.org/docs/contributed-modules/advanced-cssjs-aggregati...

Here we see that there are directories for adding config to Nginx Aegir:
https://www.drupal.org/project/barracuda/issues/1974542#comment-7320110

/var/aegir/config/server_master/nginx/vhost.d and not /var/aegir/config/server_master/nginx/pre.d for non-Drupal vhosts. The /var/aegir/config/server_master/nginx/pre.d is intended to be used only for higher level tools, like proxies etc. but not for vhosts, hence the name nginx/pre.d, while vhosts go to nginx/vhost.d

There are two more subdirectories. What are they used for?
/var/aegir/config/server_master/nginx/post.d
/var/aegir/config/server_master/nginx/subdir.d

I do not want to edit any Aegir config files as they might change.

Should config like advagg go into one of the above so as only to apply to Aegir based sites?

What is the best practice for a server based setup where there is access to /etc/nginx and /etc/nginx/conf.d and all the other directories?

If I placed config here, would it apply to all sites even non-aegir sites installed?

Should I create a file and symlink to /var/aegir/config/server_master/nginx/pre.d for example?

Or can I just place a file in /etc/nginx/conf.d?

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes