Ash should raise an error if an actor template expands to not loaded

[vkryukov]

If a policy references a field on actor that is not loaded, it might incorrectly succeed:

    policy action_type(:create) do
      forbid_if expr(^actor(:journals_at_limit?) == true)
      authorize_if always()
    end

In the above example, the :journals_at_limit? is a calculated field that evaluates to true, yet the action succeeds.

Expected behavior: an error should be raised if the field is not loaded.

[zachdaniel]

I will adjust this in the near future. However, remember to test your policies with realistic conditions folks! 😄