XMPP - Groups file population

I see that the FreePBX Distro implements the groups module for Prosody.

I am wanting to know how this file is being populated. I have not been able to figure out a definitive event that triggers this population. It seems random and not complete (at least on my install). I have some users appearing under the [users] group in this file (which I can see being pushed out to my clients), but not all of them. It would also be nice to know how to create these groups? Is this all based off the User Management module, or am I able to manually edit this file in some way? (maybe a script thats run each time ‘apply changes’ is pressed?)

Just as a side note, I have downloaded and enabled the “auto_accept_subscriptions” module for Prosody, as the system I am designing should have all users presence available at all times. I don’t want people having to manually authorise presence subscriptions on their clients. I do understand that users inside the same group do not need to authorise subscriptions, but until I can understand how the groups are populated this is a good enough work around.

Thanks for any information you can pass on!