The documentation for tasks seems to imply that the POST method uses name/value pairs as the data payload (I'm assuming for a content type of application/x-www-form-urlencoded). Can it accept JSON instead, using the same format as the data returned from a GET call for tasks?
Also, the Memberships field is supposed to contain an array of projects and sections. There's already a Projects field for a task - do those projects need to be duplicated in the list of projects for Memberships or can just the sections be included?