FEATURE: improved tag and category watching and tracking

- present tags watched on the user prefs page
- automatically watch or unwatch old topics based on watch status

New watching and tracking logic takes care of handling old topics
(either with or without read state)

When you watch a topic you now watch historically

Also removes confusing warnings from user.

app/services/user_updater.rb

@@ -6,6 +6,12 @@ class UserUpdater
     muted_category_ids: :muted
   }
 
+  TAG_NAMES = {
+    watched_tags: :watching,
+    tracked_tags: :tracking,
+    muted_tags: :muted
+  }
+
   OPTION_ATTR = [
     :email_always,
     :mailing_list_mode,
@@ -55,6 +61,10 @@ class UserUpdater
       end
     end
 
+    TAG_NAMES.each do |attribute, level|
+      TagUser.batch_set(user, level, attributes[attribute])
+    end
+
 
     save_options = false