I checked again, and no, the response from
GET index.php?/api/v2/get_case_fields does not include Milestone, Estimate, or References fields. And no, there is no information whether the field is active or hidden. I wouldn't be reporting the issue if there were.
A generic API user is hardly a workaround. First of all, sometimes it is required that the REST API call is made by a specific user (e.g. via UI script). Besides, having a dedicated API user counts toward licensing costs. I'd really suggest that you put this issue on the list and either:
a) fix the
add_result methods so that they expect specified date format, e.g. ISO 8601 (after all, REST is for machine-to-machine communication);
b) provide endpoint to determine current user's date format;
c) accept dates both in user's locale and a standard one (currently validation fails if date submitted not in user locale)
With best regards,