How can I tell the difference between BAD_REQUEST responses when I create a subscription?

Sometimes the Bango Resale API returns HTTP 400 BAD_REQUEST when you create a subscription. The responseMessage property in the response body can help you identify the reason for the response.

• If the entitlement already exists and is in ACTIVE state, then the responseMessage property is Invalid request or the request contains invalid data. Maximum number of subscriptions for user reached
• If the request is invalid, then the responseMessage is parameter is required or parameter is invalid, where parameter is the name of the parameter