Use ActiveSupport.on_load to correctly re-open ActiveRecord::Base

[iaankrynauw]

#335

I don't really know how to write a test for this. Although I have checked that it fixes the issue.

In Rails5 Rails.application.config.active_record.belongs_to_required_by_default = true gets added in new_framework_defaults.rb.

When opening ActiveRecord::Base this gets overridden and requires belongs_to model, required: true.

The fix waits for ActiveSupport.on_load(:active_record) to load before opening ActiveRecord::Base.

class ParanoidModel < ActiveRecord::Base
  belongs_to :parent_model
  acts_as_paranoid
end

expect(ParanoidModel.create).to_not be_valid
expect(ParanoidModel.create(parent_model_id: 1)).to be_valid

[BenMorganIO]

Thanks @iaankrynauw 👍