Before this commit, there was no way for us to efficiently check an
array of topics for which a user can see. Therefore, this commit
introduces the `TopicGuardian#can_see_topic_ids` method which accepts an
array of `Topic#id`s and filters out the ids which the user is not
allowed to see. The `TopicGuardian#can_see_topic_ids` method is meant to
maintain feature parity with `TopicGuardian#can_see_topic?` at all
times so a consistency check has been added in our tests to ensure that
`TopicGuardian#can_see_topic_ids` returns the same result as
`TopicGuardian#can_see_topic?`. In the near future, the plan is for us
to switch to `TopicGuardian#can_see_topic_ids` completely but I'm not
doing that in this commit as we have to be careful with the performance
impact of such a change.
This method is currently not being used in the current commit but will
be relied on in a subsequent commit.
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
