Keep edited timestamp when reacting to old notes

Copies updated_at to last_edited_at before bumping updated_at.
last_edited_at was added later and we decided not to do a backfill
migration so we just did a fallback to updated_at for old notes.

Changelog: fixed

app/models/note.rb

@@ -504,7 +504,15 @@ class Note < ApplicationRecord
     # Instead of calling touch which is throttled via ThrottledTouch concern,
     # we bump the updated_at column directly. This also prevents executing
     # after_commit callbacks that we don't need.
-    update_column(:updated_at, Time.current)
+    attributes_to_update = { updated_at: Time.current }
+
+    # Notes that were edited before the `last_edited_at` column was added, fall back to `updated_at` for the edit time.
+    # We copy this over to the correct column so we don't erroneously change the edit timestamp.
+    if updated_by_id.present? && read_attribute(:last_edited_at).blank?
+      attributes_to_update[:last_edited_at] = updated_at
+    end
+
+    update_columns(attributes_to_update)
   end
 
   def expire_etag_cache

spec/models/note_spec.rb

@@ -1685,4 +1685,27 @@ RSpec.describe Note do
       expect(note.commands_changes.keys).to contain_exactly(:emoji_award, :time_estimate, :spend_time)
     end
   end
+
+  describe '#bump_updated_at', :freeze_time do
+    it 'sets updated_at to the current timestamp' do
+      note = create(:note, updated_at: 1.day.ago)
+
+      note.bump_updated_at
+      note.reload
+
+      expect(note.updated_at).to be_like_time(Time.current)
+    end
+
+    context 'with legacy edited note' do
+      it 'copies updated_at to last_edited_at before bumping the timestamp' do
+        note = create(:note, updated_at: 1.day.ago, updated_by: create(:user), last_edited_at: nil)
+
+        note.bump_updated_at
+        note.reload
+
+        expect(note.last_edited_at).to be_like_time(1.day.ago)
+        expect(note.updated_at).to be_like_time(Time.current)
+      end
+    end
+  end
 end