Fix duplicate author showing up in autocomplete

The author was already turned into a hash before calling uniq so the
duplicates weren't filtered out.

This also adds the status preloading to the author so that it's included
when we batch load user statuses.

app/services/concerns/users/participable_service.rb

@@ -13,7 +13,9 @@ module Users
     def noteable_owner
       return [] unless noteable && noteable.author.present?
 
-      [user_as_hash(noteable.author)]
+      [noteable.author].tap do |users|
+        preload_status(users)
+      end
     end
 
     def participants_in_noteable

spec/services/projects/participants_service_spec.rb

@@ -4,17 +4,20 @@ require 'spec_helper'
 
 RSpec.describe Projects::ParticipantsService do
   describe '#execute' do
-    let(:user) { create(:user) }
-    let(:project) { create(:project, :public) }
-    let(:noteable) { create(:issue, project: project) }
+    let_it_be(:user) { create(:user) }
+    let_it_be(:project) { create(:project, :public) }
+    let_it_be(:noteable) { create(:issue, project: project) }
+
+    before_all do
+      project.add_developer(user)
+    end
 
     def run_service
       described_class.new(project, user).execute(noteable)
     end
 
+    context 'N+1 checks' do
       before do
-      project.add_developer(user)
-
         run_service # warmup, runs table cache queries and create queries
         BatchLoader::Executor.clear_current
       end
@@ -44,6 +47,13 @@ RSpec.describe Projects::ParticipantsService do
 
         expect { run_service }.not_to exceed_query_limit(control_count)
       end
+    end
+
+    it 'does not return duplicate author' do
+      participants = run_service
+
+      expect(participants.count { |p| p[:username] == noteable.author.username }).to eq 1
+    end
 
     describe 'group items' do
       subject(:group_items) { run_service.select { |hash| hash[:type].eql?('Group') } }