Issue Summary

REST API for Add user to group returns error 400 instead of 404 when the user does not exist. According to the documentation of JIRA 8.5.3 when the user or group does not exist, an error 404 should be returned.

Steps to Reproduce

Do a POST request to the endpoint /rest/api/2/group/user sending a body with an invalid use like this:

 {"name":"not.existing.user"}

Expected Results

As per documentation, "STATUS 404 Returned if the requested group was not found or requested user was not found.".

Actual Results

A message 400 is returned:

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available