Per category default watch state (and a way to reset everybody to that state)

[djensen47]

NodeBB version: 1.12.2

Feature Request

• Add a feature to each category that allows a default setting for watch state.
• Add a checkbox that allows the user to override the default or not.
• Allow admin to press a button to overwrite all user's current setting for that category (or just provide a script in the docs or something that we can run to do this).

Note: I know we currently have a setting that is global for all categories. For my use case it's not super helpful.

Motivation: there are certain types of forums that have categories that create a lot of noise. In particular, gaming site where people "play by forum." Any feature of the forum that relies on watched categories gets "spammed" by these game status posts.

[realkinetix]

This would be super helpful for a variety of cases, such as an Announcements category that people should be watching and getting announcements from, possibly by email, if they're not around the forum all that often, but perhaps not to have a default of watching on other categories as it could create too much noise.

This would mean it should be allowed to have the default on a category set to Watching, too.