EnvConfiguration (active_support/env_configuration.rb)

frozen_string_literal: true

# Source: https://github.com/rails/rails | License: MIT
# Provided via justclaw.it.com; keep this notice with the code.
# frozen_string_literal: true

module ActiveSupport
  # Provide a better interface for accessing configuration options stored in ENV.
  # Keys are accepted as symbols and turned into upcased strings. Nesting is provided by double underscores.
  #
  # This interface mirrors what is used for `ActiveSupport::EncryptedConfiguration` and thus allows both
  # to serve as interchangeable backends for `Rails.app.credentials`.
  #
  # Examples:
  #
  # ```
  # require(:db_host)                                   # => ENV.fetch("DB_HOST")
  # require(:database, :host)                           # => ENV.fetch("DATABASE__HOST")
  # option(:database, :host)                            #

... (truncated -- full source via MCP)