FIX: tag and category watchers regression (#8336)

I made a regression here 17366d3bcc (diff-ddeebb36d131f89ca91be9d04c2baefaR10)

When the tag is added, people watching specific tag are notified but also people watching specific category.

Therefore, `notify_post_users` should accept options who should be notified.

So when `category` is added to the topic, users watching topic and users watching category are notified.

When `tag` is added to the topic, users watching topic and users watching tag are notified

Finally, when a new post is created, everybody is notified, topic watchers, category watchers, tag watchers.

app/jobs/regular/notify_category_change.rb

@@ -7,7 +7,7 @@ module Jobs
 
       if post&.topic&.visible?
         post_alerter = PostAlerter.new
-        post_alerter.notify_post_users(post, User.where(id: args[:notified_user_ids]))
+        post_alerter.notify_post_users(post, User.where(id: args[:notified_user_ids]), include_tag_watchers: false)
         post_alerter.notify_first_post_watchers(post, post_alerter.category_watchers(post.topic))
       end
     end

app/jobs/regular/notify_tag_change.rb

@@ -7,7 +7,7 @@ module Jobs
 
       if post&.topic&.visible?
         post_alerter = PostAlerter.new
-        post_alerter.notify_post_users(post, User.where(id: args[:notified_user_ids]))
+        post_alerter.notify_post_users(post, User.where(id: args[:notified_user_ids]), include_category_watchers: false)
         post_alerter.notify_first_post_watchers(post, post_alerter.tag_watchers(post.topic))
       end
     end

app/services/post_alerter.rb

@@ -559,7 +559,7 @@ class PostAlerter
     end
   end
 
-  def notify_post_users(post, notified)
+  def notify_post_users(post, notified, include_category_watchers: true, include_tag_watchers: true)
     return unless post.topic
 
     warn_if_not_sidekiq
@@ -570,8 +570,14 @@ class PostAlerter
           FROM topic_users
          WHERE notification_level = :watching
            AND topic_id = :topic_id
+         /*category*/
+         /*tags*/
+      )
+    SQL
 
-         UNION
+    if include_category_watchers
+      condition.sub! "/*category*/", <<~SQL
+        UNION
 
         SELECT cu.user_id
           FROM category_users cu
@@ -580,14 +586,12 @@ class PostAlerter
          WHERE cu.notification_level = :watching
            AND cu.category_id = :category_id
            AND tu.user_id IS NULL
-
+      SQL
-        /*tags*/
+    end
-      )
-    SQL
 
     tag_ids = post.topic.topic_tags.pluck('topic_tags.tag_id')
 
-    if tag_ids.present?
+    if include_tag_watchers && tag_ids.present?
       condition.sub! "/*tags*/", <<~SQL
         UNION
 

spec/jobs/notify_tag_change_spec.rb

@@ -25,4 +25,13 @@ describe ::Jobs::NotifyTagChange do
     expect(notification.user_id).to eq(user.id)
     expect(notification.topic_id).to eq(post.topic_id)
   end
+
+  it 'doesnt create notification for user watching category' do
+    CategoryUser.create!(
+      user_id: user.id,
+      category_id: post.topic.category_id,
+      notification_level: TopicUser.notification_levels[:watching]
+    )
+    expect { described_class.new.execute(post_id: post.id, notified_user_ids: [regular_user.id]) }.not_to change { Notification.count }
+  end
 end