Ray Strode authored Aug 04, 2021 and Ray Strode committed Oct 08, 2021

At the moment there's no easy way to set a default session, or
face icon or whatever for all users.  If a user has never logged in
before, we just generate their cache file from hardcoded defaults.

This commit introduces a template system to make it possible for
admins to set up defaults on their own.

Admins can write either
/etc/accountsservice/user-templates/administrator
or
/etc/accountsservice/user-templates/standard

files.  These files follow the same format as

/var/lib/AccountsService/users/username

files, but will support substituting $HOME and $USER to the appropriate
user specific values.

User templates also support an additional group [Template] that
have an additional key EnvironmentFiles that specify a list
of environment files to load (files with KEY=VALUE pairs in them).
Any keys listed in those environment files will also get substituted.

#63