Exclude guests being billable for ultimate trials

Guests users are not considered billable for ultimate plan customers,
this change applies the same logic to ultimate trial customers

Changelog: changed
EE: true

ee/app/models/ee/group.rb

@@ -349,7 +349,7 @@ module EE
     # For the user_ids key, we are plucking the user_ids from the "Members" table in an array and
     # converting the array of user_ids to a Set which will have unique user_ids.
     def billed_user_ids(requested_hosted_plan = nil)
-      exclude_guests = ([actual_plan_name, requested_hosted_plan] & [::Plan::GOLD, ::Plan::ULTIMATE]).any?
+      exclude_guests = ([actual_plan_name, requested_hosted_plan] & [::Plan::GOLD, ::Plan::ULTIMATE, ::Plan::ULTIMATE_TRIAL]).any?
 
       exclude_guests ? billed_user_ids_excluding_guests : billed_user_ids_including_guests
     end

ee/spec/models/ee/namespace_spec.rb

@@ -978,11 +978,7 @@ RSpec.describe Namespace do
           ])
         end
 
-        context 'with a ultimate plan' do
-          before do
-            create(:gitlab_subscription, namespace: group, hosted_plan: ultimate_plan)
-          end
-
+        shared_examples 'ultimate plan' do
           it 'does not include guest users and only active users' do
             expect(billed_user_ids[:user_ids]).to match_array([developer.id])
           end
@@ -1118,6 +1114,22 @@ RSpec.describe Namespace do
           end
         end
 
+        context 'with a ultimate plan' do
+          before do
+            create(:gitlab_subscription, :ultimate, namespace: group)
+          end
+
+          it_behaves_like 'ultimate plan'
+        end
+
+        context 'with an ultimate trial plan' do
+          before do
+            create(:gitlab_subscription, :ultimate_trial, namespace: group)
+          end
+
+          it_behaves_like 'ultimate plan'
+        end
+
         context 'with other plans' do
           %i[bronze_plan premium_plan].each do |plan|
             subject(:billed_user_ids) { group.billed_user_ids }