Log arguments of event store subscriber

Ensure we log string arguments the subscribers receives.
Remove the need to `include ApplicationWorker` for each
subscriber. We now include ApplicationWorker once in the
EventStore::Subscriber class.

app/workers/merge_requests/update_head_pipeline_worker.rb

@@ -2,7 +2,6 @@
 
 module MergeRequests
   class UpdateHeadPipelineWorker
-    include ApplicationWorker
     include Gitlab::EventStore::Subscriber
 
     feature_category :code_review

doc/development/event_store.md

@@ -232,7 +232,6 @@ the event safely via the `handle_event` method. For example:
 ```ruby
 module MergeRequests
   class UpdateHeadPipelineWorker
-    include ApplicationWorker
     include Gitlab::EventStore::Subscriber
 
     def handle_event(event)

ee/app/workers/gitlab_subscriptions/notify_seats_exceeded_worker.rb

@@ -2,7 +2,6 @@
 
 module GitlabSubscriptions
   class NotifySeatsExceededWorker
-    include ApplicationWorker
     include Gitlab::EventStore::Subscriber
 
     feature_category :purchase

lib/gitlab/event_store/subscriber.rb

@@ -7,7 +7,6 @@
 #
 # @example:
 #   class SomeEventSubscriber
-#     include ApplicationWorker
 #     include Gitlab::EventStore::Subscriber
 #
 #     def handle_event(event)
@@ -18,6 +17,14 @@
 module Gitlab
   module EventStore
     module Subscriber
+      extend ActiveSupport::Concern
+
+      included do
+        include ApplicationWorker
+
+        loggable_arguments 0, 1
+      end
+
       def perform(event_type, data)
         raise InvalidEvent, event_type unless self.class.const_defined?(event_type)
 

spec/lib/gitlab/event_store/store_spec.rb

@@ -10,7 +10,6 @@ RSpec.describe Gitlab::EventStore::Store do
   let(:worker) do
     stub_const('EventSubscriber', Class.new).tap do |klass|
       klass.class_eval do
-        include ApplicationWorker
         include Gitlab::EventStore::Subscriber
 
         def handle_event(event)
@@ -23,7 +22,6 @@ RSpec.describe Gitlab::EventStore::Store do
   let(:another_worker) do
     stub_const('AnotherEventSubscriber', Class.new).tap do |klass|
       klass.class_eval do
-        include ApplicationWorker
         include Gitlab::EventStore::Subscriber
       end
     end
@@ -32,7 +30,6 @@ RSpec.describe Gitlab::EventStore::Store do
   let(:unrelated_worker) do
     stub_const('UnrelatedEventSubscriber', Class.new).tap do |klass|
       klass.class_eval do
-        include ApplicationWorker
         include Gitlab::EventStore::Subscriber
       end
     end
@@ -253,6 +250,10 @@ RSpec.describe Gitlab::EventStore::Store do
 
     subject { worker_instance.perform(event_name, data) }
 
+    it 'is a Sidekiq worker' do
+      expect(worker_instance).to be_a(ApplicationWorker)
+    end
+
     it 'handles the event' do
       expect(worker_instance).to receive(:handle_event).with(instance_of(event.class))