FEATURE: Track last_viewed_at datetime for channel members (#22294)

Whenever a user opens a channel or marks it read, we now
update the last_viewed_at datetime for that channel membership
record. This is so we will be able to show thread unread indicators
in the channel sidebar that clear independently of the main thread
unread indicators. This unread functionality will follow in another
PR.

plugins/chat/spec/services/chat/channel_view_builder_spec.rb

@@ -37,6 +37,8 @@ RSpec.describe Chat::ChannelViewBuilder do
       }
     end
 
+    before { channel.add(current_user) }
+
     it "threads_enabled is false by default" do
       expect(result.threads_enabled).to eq(false)
     end
@@ -76,6 +78,14 @@ RSpec.describe Chat::ChannelViewBuilder do
       )
     end
 
+    it "updates the channel membership last_viewed_at" do
+      membership = channel.membership_for(current_user)
+      membership.update!(last_viewed_at: 1.day.ago)
+      old_last_viewed_at = membership.last_viewed_at
+      result
+      expect(membership.reload.last_viewed_at).not_to eq_time(old_last_viewed_at)
+    end
+
     it "does not query thread tracking overview or state by default" do
       Chat::TrackingStateReportQuery.expects(:call).never
       result

plugins/chat/spec/services/chat/update_user_last_read_spec.rb

@@ -109,6 +109,13 @@ RSpec.describe Chat::UpdateUserLastRead do
         it "publishes new last read to clients" do
           expect(messages.map(&:channel)).to include("/chat/user-tracking-state/#{current_user.id}")
         end
+
+        it "updates the channel membership last_viewed_at datetime" do
+          membership.update!(last_viewed_at: 1.day.ago)
+          old_last_viewed_at = membership.last_viewed_at
+          result
+          expect(membership.reload.last_viewed_at).not_to eq_time(old_last_viewed_at)
+        end
       end
     end
   end