BlipPayload

BlipPayload = BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object | BlipPayloadCommon & object

One blip.update message: a complete, self-describing snapshot of one item. layout and data are a discriminated union: narrow on layout to get the matching data shape.