NOTE: Creating Postback type will be affected by the types of conversion_protocol.
conversion_protocol：1:Image Pixel; 2:postback url; 3:HTML Pixel
When offer’s conversion_protocol=1, Postback type can be set as 1 or 2.
When offer’s conversion_protocol=2, Postback type can be only set as 2.
When offer’s conversion_protocol=3, Postback type will not be limited, and it can be set as 1, 2 or 3.
When setting global postback (offer_id=0), postback type will be not limited, and it can be set as 1, 2 or 3.
Create Postback for an offer
Get All Postbacks
Get a Postback by id
Delete a Postback by id