post https://app.asana.com/api/1.0/projects//addMembers
Adds the specified list of users as members of the project. Note that a user being added as a member may also be added as a follower as a result of this operation. This is because the user's default notification settings (i.e., in the "Notifications" tab of "My Profile Settings") will override this endpoint's default behavior of setting "Tasks added" notifications to false.
Returns the updated project record.