Fix issue's note cache expiration after delete

app/models/note.rb

@@ -96,6 +96,7 @@ class Note < ActiveRecord::Base
   before_validation :set_discussion_id, on: :create
   after_save :keep_around_commit, unless: :for_personal_snippet?
   after_save :expire_etag_cache
+  after_destroy :expire_etag_cache
 
   class << self
     def model_name

changelogs/unreleased/30457-expire-note-destroy.yml

+---
+title: Fix issue's note cache expiration after delete
+merge_request:
+author: mhasbini

spec/models/note_spec.rb

@@ -622,12 +622,22 @@ describe Note, models: true do
   describe 'expiring ETag cache' do
     let(:note) { build(:note_on_issue) }
 
-    it "expires cache for note's issue when note is saved" do
+    def expect_expiration(note)
       expect_any_instance_of(Gitlab::EtagCaching::Store)
         .to receive(:touch)
         .with("/#{note.project.namespace.to_param}/#{note.project.to_param}/noteable/issue/#{note.noteable.id}/notes")
+    end
+
+    it "expires cache for note's issue when note is saved" do
+      expect_expiration(note)
 
       note.save!
     end
+
+    it "expires cache for note's issue when note is destroyed" do
+      expect_expiration(note)
+
+      note.destroy!
+    end
   end
 end