Easier usage of Rails 5.2 credentials and app-specific configuration

As you all know by now, Rails 5.2 introduced a new feature called Credentials. DHH said the following in the PR:This new file is a flat format, not divided by environments like secrets.yml has been. Most of the time, these credentials are only relevant in production, and if someone does need to have some keys duplicated for different environments, it can be done by hand.