Propose to mention The Twelve-Factor App as a reference in the configuring.html section of the Rails Guide

Hi All.

The content covered in ‘Creating Rails Environments’ often seems like painful practices as the application is growing.

The actual problems I have experienced are listed below:

  • Often there are differences in the settings of staging.rb and production.rb by mistake, leading to behavioral differences between the production environment and the staging environment, which can be time-consuming to investigate.
  • if Rails.env.production? , causing a behavioral discrepancy between the staging environment and the production environment, where things work fine in the staging environment but have problems in the production environment.
  • etc.

I think it would be a good idea to include a link to The Twelve-Factor App as a reference for people who are developing production-quality applications in Rails, don’t you?

For example, a TIP block like the following:

TIP: For more reliable and larger applications, consider using environment variables instead of `staging.rb` as described here to deal with differences between environments.
The Twelve-Factor App's [III. Config](https://12factor.net/config) will help you as a good reference.