Improve parallel persistance for audit event author_name

On verification of https://gitlab.com/gitlab-org/gitlab/-/issues/220318
we discovered that some audit events were not created with
author_name populated correctly.

This approach saves the author_name as an AR callback instead.

app/models/audit_event.rb

@@ -19,7 +19,15 @@ class AuditEvent < ApplicationRecord
   scope :by_entity_id, -> (entity_id) { where(entity_id: entity_id) }
   scope :by_author_id, -> (author_id) { where(author_id: author_id) }
 
+  PARALLEL_PERSISTENCE_COLUMNS = [:author_name].freeze
+
   after_initialize :initialize_details
+  # Note: The intention is to remove this once refactoring of AuditEvent
+  # has proceeded further.
+  #
+  # See further details in the epic:
+  # https://gitlab.com/groups/gitlab-org/-/epics/2765
+  after_validation :parallel_persist
 
   def self.order_by(method)
     case method.to_s
@@ -55,6 +63,10 @@ class AuditEvent < ApplicationRecord
   def default_author_value
     ::Gitlab::Audit::NullAuthor.for(author_id, (self[:author_name] || details[:author_name]))
   end
+
+  def parallel_persist
+    PARALLEL_PERSISTENCE_COLUMNS.each { |col| self[col] = details[col] }
+  end
 end
 
 AuditEvent.prepend_if_ee('EE::AuditEvent')

ee/spec/models/audit_event_spec.rb

@@ -28,6 +28,14 @@ RSpec.describe AuditEvent, type: :model do
     end
   end
 
+  describe 'callbacks' do
+    it 'sets author_name' do
+      event = create(:user_audit_event, details: { author_name: 'Kungfu Panda' })
+
+      expect(event[:author_name]).to eq('Kungfu Panda')
+    end
+  end
+
   describe '.order_by' do
     let_it_be(:event_1) { create(:audit_event) }
     let_it_be(:event_2) { create(:audit_event) }

ee/spec/presenters/audit_event_presenter_spec.rb

@@ -61,12 +61,6 @@ RSpec.describe AuditEventPresenter do
         end
       end
 
-      context 'when author_name is set in the author_name column' do
-        it 'shows the author name as provided in the database column' do
-          expect(presenter.author_name).to eq('Jane Doe')
-        end
-      end
-
       context 'when `author_name` is included in the details and not in the author_name column' do
         before do
           audit_event.update!(author_name: nil)

ee/spec/services/audit_event_service_spec.rb

@@ -11,15 +11,14 @@ RSpec.describe AuditEventService do
   let(:service) { described_class.new(user, project, details) }
 
   describe '#for_member' do
+    let(:event) { service.for_member(project_member).security_event }
+
     it 'generates event' do
-      event = service.for_member(project_member).security_event
       expect(event[:details][:target_details]).to eq(user.name)
     end
 
     it 'handles deleted users' do
       expect(project_member).to receive(:user).and_return(nil)
-
-      event = service.for_member(project_member).security_event
       expect(event[:details][:target_details]).to eq('Deleted User')
     end
 
@@ -27,14 +26,21 @@ RSpec.describe AuditEventService do
       let(:service) { described_class.new(nil, project, { action: :expired }) }
 
       it 'generates a system event' do
-        event = service.for_member(project_member).security_event
-
         expect(event[:details][:remove]).to eq('user_access')
         expect(event[:details][:system_event]).to be_truthy
         expect(event[:details][:reason]).to include('access expired on')
       end
     end
 
+    context 'create user access' do
+      let(:details) { { action: :create } }
+
+      it 'stores author name', :aggregate_failures do
+        expect(event.details[:author_name]).to eq(user.name)
+        expect(event.author_name).to eq(user.name)
+      end
+    end
+
     context 'updating membership' do
       let(:service) do
         described_class.new(user, project, {
@@ -273,6 +279,7 @@ RSpec.describe AuditEventService do
 
     it 'has the right author' do
       expect(event.details[:author_name]).to eq(author_name)
+      expect(event.author_name).to eq(author_name)
     end
 
     it 'has the right target_details' do