No way to access parent Epic from Epic API details

Proposal

In the Epics API fetching a list of epics returns the epics id, iid and the parent_id, To fetch a single Epic you need to use the iid of it, so you can then access epics/${iid} but there is no way to access epics/$[parent_iid} since that is not returned in the API.

Adding the parent_iid to the response would be great. Including a parent key into _links would also be really nice.