Properly file_store default for pages deployments

create!(file: somefile) actually assigns file before
default_valud_for works. So Pages::DeploymentUploader
gets the wrong default from the model and will always
save file to disk storage regardless of object storage
being enabled.

rails attributes api actually allows to set default properly

app/models/pages_deployment.rb

@@ -4,6 +4,8 @@
 class PagesDeployment < ApplicationRecord
   include FileStoreMounter
 
+  attribute :file_store, :integer, default: -> { ::Pages::DeploymentUploader.default_store }
+
   belongs_to :project, optional: false
   belongs_to :ci_build, class_name: 'Ci::Build', optional: true
 
@@ -17,8 +19,6 @@ class PagesDeployment < ApplicationRecord
 
   before_validation :set_size, if: :file_changed?
 
-  default_value_for(:file_store) { ::Pages::DeploymentUploader.default_store }
-
   mount_file_store_uploader ::Pages::DeploymentUploader
 
   private

spec/factories/pages_deployments.rb

@@ -5,7 +5,7 @@ FactoryBot.define do
     project
 
     after(:build) do |deployment, _evaluator|
-      filepath =  Rails.root.join("spec/fixtures/pages.zip")
+      filepath = Rails.root.join("spec/fixtures/pages.zip")
 
       deployment.file = fixture_file_upload(filepath)
       deployment.file_sha256 = Digest::SHA256.file(filepath).hexdigest

spec/models/pages_deployment_spec.rb

@@ -27,14 +27,26 @@ RSpec.describe PagesDeployment do
   end
 
   describe 'default for file_store' do
+    let(:project) { create(:project) }
+    let(:deployment) do
+      filepath = Rails.root.join("spec/fixtures/pages.zip")
+
+      described_class.create!(
+        project: project,
+        file: fixture_file_upload(filepath),
+        file_sha256: Digest::SHA256.file(filepath).hexdigest,
+        file_count: 3
+      )
+    end
+
     it 'uses local store when object storage is not enabled' do
-      expect(build(:pages_deployment).file_store).to eq(ObjectStorage::Store::LOCAL)
+      expect(deployment.file_store).to eq(ObjectStorage::Store::LOCAL)
     end
 
     it 'uses remote store when object storage is enabled' do
       stub_pages_object_storage(::Pages::DeploymentUploader)
 
-      expect(build(:pages_deployment).file_store).to eq(ObjectStorage::Store::REMOTE)
+      expect(deployment.file_store).to eq(ObjectStorage::Store::REMOTE)
     end
   end