Disable strict loading on ActiveStorage::Attached::Changes

[Roriz]

Summary

When we try to attach a new file with strict_loading_by_default = true on the model, will always raise an ActiveRecord::StrictLoadingViolationError because of validation of active storage (https://github.com/rails/rails/blob/main/activestorage/lib/active_storage/attached/changes/create_one.rb#L43).
This validation is trigger always without loading any association (https://github.com/rails/rails/blob/main/activestorage/lib/active_storage/attached/model.rb#L65)

In past, we already disable strict_loading on validations(#40775), but active_storage still keeps this validation. This PR disable strict_loading on save of Attached::Changes::CreateOne

This PR solves the issue: #41453

Setup

rails new sl-with-as --database=postgresql --no-skip-active-storage
cd sl-with-as/
rails active_storage:install
rails generate model Example name:string
rails db:create && rails db:migrate
echo 'class Example < ActiveRecord::Base; self.strict_loading_by_default = true; has_one_attached :file; end' > app/models/example.rb
rails console
example = Example.create(name: 'Lorem')
example.file.attach({ io: File.new("tmp/temp1.txt"), filename: 'tempfile1' }) # ActiveRecord::StrictLoadingViolationError

[andersonmarcelino]

LGTM

[eileencodes]

Hi @Roriz thanks for the PR and the issue - I combined your test changes here into the suggestion on the issue in #41688. This was a bug with any relation not just active storage. I made sure to add your authorship so you get credit for the change.