def secret_key_base
      if Rails.env.development? || Rails.env.test?
        secrets.secret_key_base ||= generate_development_secret
      else
        validate_secret_key_base(
          ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
        )
      end
    end
def secret_key_base
      if Rails.env.development? || Rails.env.test?
        secrets.secret_key_base ||= generate_development_secret
      else
        validate_secret_key_base(
          ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
        )
      end
    end
The secret_key_base is used as the input secret to the application's key generator, which in turn
 is used to create all MessageVerifiers/MessageEncryptors, including the ones that sign and encrypt cookies.

 In development and test, this is randomly generated and stored in a
 temporary file in <tt>tmp/development_secret.txt</tt>.

 In all other environments, we look for it first in ENV["SECRET_KEY_BASE"],
 then credentials.secret_key_base, and finally secrets.secret_key_base. For most applications,
 the correct place to store it is in the encrypted credentials file.