"due_date" parameter is missing in the issues API.

In the HAML version of the issues list, we can filter for the issues due in a time period. For example, we can enter https://gitlab.com/gitlab-org/gitlab/-/issues?due_date=week to retrieve the issues due in the current week.

The group issues API does not have due_date attribute: https://docs.gitlab.com/ee/api/issues.html#list-group-issues. So we cannot currently filter by the due dates using the public API like this: http://127.0.0.1:3000/api/v4/groups/52/issues?due_date=week

This was discovered while updating an rspec to turn on the feature flag :vue_issuables_list !38423 (comment 389217200)