As someone who has spent far too much time thinking about managing configuration and secrets in Rails applications, this post from Joy of Rails is solid.
Learn how to use “Rails config x” and add your own configuration options to your Rails app with built-in methods, ActiveSupport::OrderedOptions, and practical use cases.
Rails provides a plethora of great tools for managing configurable values, environment variables, credentials/secrets, and even per-environment variations. Like generators, while Rails uses them plenty internally, all of these tools are equally available and accessible for our own custom configuration bits.