Make members of a group watch a category by default

[galligan (Matt Galligan)]

FYI this has now been updated by @LeoMcA. See:

@LeoMcA

I needed to implement a subset of these features in a different plugin I’m working on, so decided to spin them out as a separate plugin, as even in this early stage it may prove useful to others (and it makes building upon them, and implementing this whole spec, easier in future):

GitHub - mozilla/discourse-group-category-notification: INACTIVE - http://mzl.la/ghe-archive - A plugin to enable automatic subscription to categories based on group membership

The readme explains a lot of the caveats, the biggest of which is probably the lack of a UI.