Drop system notes filter and use basic scope

app/models/concerns/issuable.rb

@@ -73,15 +73,8 @@ module Issuable
       end
     end
 
-    has_many :note_authors, -> { distinct }, through: :notes, source: :author do
-      def user_notes
-        where("notes.system = false")
-      end
-
-      def system_notes
-        where("notes.system = true")
-      end
-    end
+    has_many :note_authors, -> { distinct }, through: :notes, source: :author
+    has_many :user_note_authors, -> { distinct.where("notes.system = false") }, through: :notes, source: :author
 
     has_many :label_links, as: :target, inverse_of: :target
     has_many :labels, through: :label_links

spec/models/concerns/issuable_spec.rb

@@ -29,29 +29,20 @@ RSpec.describe Issuable do
       end
 
       describe 'note_authors' do
+        it { is_expected.to have_many(:note_authors).through(:notes) }
+      end
+
+      describe 'user_note_authors' do
         let(:system_user) { create(:user) }
         let!(:system_note) { create(:system_note, author: system_user, noteable: issue, project: issue.project) }
 
-        it { is_expected.to have_many(:note_authors).through(:notes) }
-
-        describe 'note_authors.user_notes' do
         it 'filters the authors to those of user notes' do
-            authors = issue.note_authors.user_notes
+          authors = issue.user_note_authors
 
           expect(authors).to include(note.author)
           expect(authors).not_to include(system_user)
         end
       end
-
-        describe 'note_authors.system_notes' do
-          it 'filters the authors to those of system notes' do
-            authors = issue.note_authors.system_notes
-
-            expect(authors).to include(system_user)
-            expect(authors).not_to include(note.author)
-          end
-        end
-      end
     end
   end