This method retrieves user information, given a user name or member ID.
Return Value: RestMember
- If the member key is missing, the call will return HTTP status code 400, bad request.
- If the user cannot be found, or if you attempt to retrieve a user for a client ID other than your own, the call will return HTTP status code 404, not found.
- An unexpected exception will return HTTP status code 500, internal server error.