Bugs

Using override(:foo) with the same :foo multiple times probably shouldn't be supported and feels a bit like wandering into undefined behavior.

Expected outcome

I guess I expected it to raise an error.

Actual outcome

🤷‍♂ didn't dig in

Config

    SecureHeaders::Configuration.override(:preview_policy) do |config|
      #...
    end

    SecureHeaders::Configuration.override(:preview_policy) do |config|
      # a different ...
    end

Generated headers

🤷‍♂ didn't dig in. This feels non-controversial enough.