FEATURE: New way to dismiss new topics (#11927)

This is a try to simplify logic around dismiss new topics to have one solution to work in all places - dismiss all-new, dismiss new in a specific category or even in a specific tag.

spec/models/topic_tracking_state_spec.rb

@@ -563,7 +563,7 @@ describe TopicTrackingState do
     end
   end
 
-  it "correctly handles seen categories" do
+  it "correctly handles dismissed topics" do
     freeze_time 1.minute.ago
     user = Fabricate(:user)
     post
@@ -571,6 +571,7 @@ describe TopicTrackingState do
     report = TopicTrackingState.report(user)
     expect(report.length).to eq(1)
 
+    DismissedTopicUser.create!(user_id: user.id, topic_id: post.topic_id, created_at: Time.zone.now)
     CategoryUser.create!(user_id: user.id,
                          notification_level: CategoryUser.notification_levels[:regular],
                          category_id: post.topic.category_id,
@@ -579,12 +580,6 @@ describe TopicTrackingState do
 
     report = TopicTrackingState.report(user)
     expect(report.length).to eq(0)
-
-    unfreeze_time
-    post.topic.touch(:created_at)
-
-    report = TopicTrackingState.report(user)
-    expect(report.length).to eq(1)
   end
 
   it "correctly handles capping" do