Get my notification preferences

The channels the logged in user can get notifications on (channels, in the preferences page's order, with their labels in the request's language): in-app when the app has a notification center, email, and those a client adds (e.g. push notifications, once they have a device to send them to). Then, for each category of notifications this app sends, whether they get it on each channel that delivers it (channels, by ID; categories they haven't changed have the channel's defaults), and the channels that always deliver it (alwaysOn: security notifications are always emailed)