Create dimension conversion rate mapping

Create a new dimension conversion rate mapping. This object creation may trigger the deletion of other existing mappings if the new object's fields would cause a conflict with those mappings. Will result in a response of 409 (Conflict), and require an additional query parameter confirm=true in the request to proceed with creating the mapping and deleting the existing mappings that conflict.Clients that receive a 200 OK response for an create should subsequently request the mappings list to learn of any deletions.