Filters whether a user can access a specific form, and optionally submission.
(bool|awsmug\Torro_Forms\Error) (Optional) Whether a user can access the form. Can be an error object to show a specific message to the user.
(awsmug\Torro_Forms\DB_Objects\Forms\Form) (Optional) Form object.
(awsmug\Torro_Forms\DB_Objects\Submissions\Submission|null) (Optional) Submission object, or null if no submission is set.