If the selected group to not display ads to had its visibility set to
not be visible then this setting wouldn't work correctly because that
group wouldn't be available client side. The change moves that group
check to be server side so that we can correctly see all the groups that
should not see ads.
* DEV: Convert TL settings to groups
This change converts the TL site settings in this plugin to use groups
instead.
See: https://meta.discourse.org/t/283408
Co-authored-by: Martin Brennan <martin@discourse.org>