Optimize generic specs for services

spec/requests/api/services_spec.rb

 require "spec_helper"
 
 describe API::Services do
-  let(:user) { create(:user) }
-  let(:admin) { create(:admin) }
-  let(:user2) { create(:user) }
-  let(:project) { create(:project, creator_id: user.id, namespace: user.namespace) }
+  set(:user) { create(:user) }
+  set(:admin) { create(:admin) }
+  set(:user2) { create(:user) }
+
+  set(:project) do
+    create(:project, creator_id: user.id, namespace: user.namespace)
+  end
 
   Service.available_services_names.each do |service|
     describe "PUT /projects/:id/services/#{service.dasherize}" do
@@ -98,8 +101,6 @@ describe API::Services do
   end
 
   describe 'POST /projects/:id/services/:slug/trigger' do
-    let!(:project) { create(:project) }
-
     describe 'Mattermost Service' do
       let(:service_name) { 'mattermost_slash_commands' }