Workaround for clients that always need 200 HTTP status code returned (e.g. Flash)
400 Bad Request: The request was invalid for reasons other than authentication.
401 Unauthorized: Authentication credentials were missing or incorrect.
Returned from POST /oauth/access_token if client_id, username, password are missing or incorrect
Returned from any authenticated request that is missing the access_token
403 Forbidden: The request is understood, but was refused because the requestor does not have the correct rights to perform the action requested.
404 Not Found: A specified instance of a resource that does not exist has been requested. Note: incorrect parameters for a request will result in a 400 response.
500 Internal Server Error: Something unexpected happened on the server. Contact support.
503 Service Unavailable: Groupon is currently unavailable to fulfill your request.
** All non-200 responses contain the standard response body that will explain the error.