Return unique schedules for member user

Move changleog

ee/app/serializers/ee/member_user_entity.rb

@@ -8,6 +8,10 @@ module EE
       unexpose :gitlab_employee
       unexpose :email
       expose :oncall_schedules, with: ::IncidentManagement::OncallScheduleEntity
+
+      def oncall_schedules
+        object.oncall_schedules.uniq
+      end
     end
   end
 end

ee/spec/serializers/member_user_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MemberUserEntity do
+  let_it_be_with_reload(:user) { create(:user) }
+
+  let(:entity) { described_class.new(user) }
+  let(:entity_hash) { entity.as_json }
+
+  it 'matches json schema' do
+    expect(entity.to_json).to match_schema('entities/member_user')
+  end
+
+  context 'with oncall schedules' do
+    let_it_be(:oncall_schedule) { create(:incident_management_oncall_participant, user: user).rotation.schedule }
+
+    it 'correctly exposes `oncall_schedules`' do
+      expect(entity_hash[:oncall_schedules]).to include(schedule_hash(oncall_schedule))
+    end
+
+    it 'exposed and de-dupes the schedules' do
+      allow(user).to receive(:oncall_schedules).and_return([oncall_schedule, oncall_schedule])
+
+      expect(entity_hash[:oncall_schedules].size).to eq(1)
+      expect(entity_hash[:oncall_schedules]).to include(schedule_hash(oncall_schedule))
+    end
+
+    def schedule_hash(schedule)
+      schedule_url = Gitlab::Routing.url_helpers.project_incident_management_oncall_schedules_url(schedule.project)
+      project_url = Gitlab::Routing.url_helpers.project_url(schedule.project)
+      {
+        name: oncall_schedule.name,
+        project_name: oncall_schedule.project.name,
+        schedule_url: schedule_url,
+        project_url: project_url
+      }
+    end
+  end
+end