adding tests for `User.needing_reminder_email`
renaming `AnswerSet.from_last_set_for` method to `from_last_set_for_user`
adding permissions checks to metrics index view
adding test for `AnswerSet.from_last_set_for_user`
flattening the accessible_cohort_ids array in the accessible_users method
typo in local variable assignment in `AnswerSet.for_index` when filtering on to_date