Get all responses for a specific invitation, with optional status filtering, sorting and paging.

Rows for anonymous responses, and on an anonymous tracking link rows for contacts who have not responded yet, carry nothing that identifies the contact or leads to their response: id, response_id, opted_out, started_survey and ended_survey are left out, and name, email and ip_address are blank. Filtering by the opted-out status does not return these rows.

Sort with sort_by set to id, response_id, started_survey or ended_survey, followed by ,asc or ,desc; repeat it to break ties. Other keys are ignored and the default, id,asc, applies. Anonymous rows have none of these values, so every sort keeps them together as one group rather than placing them by their contact, their response or when they responded. They sort with the rows that have no value for the sort key, which come first in ascending order and last in descending order.