Add members added event and start broadcasting

We want to be able to react to changes in the quantity of users in a
group. Start broadcasting a members added event in the create member
service so that we can listen for these events async.

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/348487
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/79291

app/events/members/members_added_event.rb

+# frozen_string_literal: true
+
+module Members
+  class MembersAddedEvent < ::Gitlab::EventStore::Event
+    def schema
+      {
+        'type' => 'object',
+        'required' => %w[source_id source_type],
+        'properties' => {
+          'source_id' => { 'type' => 'integer' },
+          'source_type' => { 'type' => 'string' }
+        }
+      }
+    end
+  end
+end

app/services/members/create_service.rb

@@ -24,6 +24,9 @@ module Members
 
       add_members
       enqueue_onboarding_progress_action
+
+      publish_event!
+
       result
     rescue BlankInvitesError, TooManyInvitesError, MembershipLockedError => e
       error(e.message)
@@ -144,6 +147,15 @@ module Members
     def formatted_errors
       errors.to_sentence
     end
+
+    def publish_event!
+      Gitlab::EventStore.publish(
+        Members::MembersAddedEvent.new(data: {
+          source_id: source.id,
+          source_type: source.class.name
+        })
+      )
+    end
   end
 end
 

config/sidekiq_queues.yml

@@ -177,6 +177,8 @@
   - 1
 - - gitlab_shell
   - 2
+- - gitlab_subscriptions_notify_seats_exceeded
+  - 1
 - - group_destroy
   - 1
 - - group_export

ee/app/workers/all_queues.yml

@@ -1020,6 +1020,15 @@
   :weight: 1
   :idempotent:
   :tags: []
+- :name: gitlab_subscriptions_notify_seats_exceeded
+  :worker_name: GitlabSubscriptions::NotifySeatsExceededWorker
+  :feature_category: :purchase
+  :has_external_dependencies: true
+  :urgency: :low
+  :resource_boundary: :unknown
+  :weight: 1
+  :idempotent: true
+  :tags: []
 - :name: group_saml_group_sync
   :worker_name: GroupSamlGroupSyncWorker
   :feature_category: :authentication_and_authorization

ee/app/workers/gitlab_subscriptions/notify_seats_exceeded_worker.rb

+# frozen_string_literal: true
+
+module GitlabSubscriptions
+  class NotifySeatsExceededWorker
+    include ApplicationWorker
+    include Gitlab::EventStore::Subscriber
+
+    feature_category :purchase
+    data_consistency :delayed
+    deduplicate :until_executing, including_scheduled: true
+
+    idempotent!
+    worker_has_external_dependencies!
+
+    def handle_event(event)
+      # no-op for now, to be implemented in https://gitlab.com/gitlab-org/gitlab/-/issues/348487
+    end
+  end
+end

ee/lib/ee/gitlab/event_store.rb

@@ -22,6 +22,8 @@ module EE
 
           ###
           # Add EE only subscriptions here:
+
+          store.subscribe ::GitlabSubscriptions::NotifySeatsExceededWorker, to: ::Members::MembersAddedEvent
         end
       end
     end

ee/spec/lib/gitlab/event_store_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::EventStore do
+  describe '.instance' do
+    it 'returns a store with CE and EE subscriptions' do
+      instance = described_class.instance
+
+      expect(instance.subscriptions.keys).to include(
+        ::Ci::PipelineCreatedEvent,
+        ::Members::MembersAddedEvent
+      )
+    end
+  end
+end

spec/services/members/create_service_spec.rb

@@ -39,6 +39,15 @@ RSpec.describe Members::CreateService, :aggregate_failures, :clean_gitlab_redis_
         expect(source.users).to include member
         expect(OnboardingProgress.completed?(source, :user_added)).to be(true)
       end
+
+      it 'triggers a members added event' do
+        expect(Gitlab::EventStore)
+          .to receive(:publish)
+          .with(an_instance_of(Members::MembersAddedEvent))
+          .and_call_original
+
+        expect(execute_service[:status]).to eq(:success)
+      end
     end
   end