Create CAPTCHA challenge
From ePrize Developers Wiki
Request representation: empty Response: 201 Created Location: /v1/{apikey}/captcha/{challenge-id} <?xml version="1.0" encoding="UTF-8" ?> <result>1</result> Response if CAPTCHA can not be created: 503 Service Unavailable
Note: some user have had difficulty with empty POST requests. Adding a random name/value pair (foo=foo) to the request representation can avoid this problem.