Add OncallScheduleEntity with data to members

- Preload associations

ee/app/models/ee/members_preloader.rb

@@ -9,6 +9,7 @@ module EE
       super
 
       ActiveRecord::Associations::Preloader.new.preload(members.map(&:user), group_saml_identities: :saml_provider)
+      ActiveRecord::Associations::Preloader.new.preload(members.map(&:user), oncall_participants: { rotation: :schedule })
     end
   end
 end

ee/app/models/ee/user.rb

@@ -73,6 +73,10 @@ module EE
 
       has_many :user_permission_export_uploads
 
+      has_many :oncall_participants, class_name: 'IncidentManagement::OncallParticipant', inverse_of: :user
+      has_many :oncall_rotations, class_name: 'IncidentManagement::OncallRotation', through: :oncall_participants, source: :rotation
+      has_many :oncall_schedules, class_name: 'IncidentManagement::OncallSchedule', through: :oncall_rotations, source: :schedule
+
       scope :not_managed, ->(group: nil) {
         scope = where(managing_group_id: nil)
         scope = scope.or(where.not(managing_group_id: group.id)) if group

ee/app/models/incident_management/oncall_schedule.rb

@@ -22,6 +22,10 @@ module IncidentManagement
 
     scope :for_iid, -> (iid) { where(iid: iid) }
 
+    def project_name
+      project.name
+    end
+
     private
 
     def timezones

ee/app/serializers/ee/member_user_entity.rb

@@ -7,6 +7,7 @@ module EE
     prepended do
       unexpose :gitlab_employee
       unexpose :email
+      expose :oncall_schedules, with: ::IncidentManagement::OncallScheduleEntity
     end
   end
 end

ee/app/serializers/incident_management/oncall_schedule_entity.rb

+# frozen_string_literal: true
+
+module IncidentManagement
+  class OncallScheduleEntity < Grape::Entity
+    expose :name
+    expose :project_name
+  end
+end