Is this proposal intended to replace the current model of `extended` as a Boolean, with `extendedDelivery` containing the value of the extended amount? Or will we translate into that data model for e.g., blip/tideline?

I think the `extended` as a Boolean model makes some sense considering that we have things like users delivering normal boluses via the combo/extended bolus menu. These things have `extended` as true as a sort of meta-identifier of how they were generated, but we end up identifying them (via `extendedDelivery === 0`) and visualizing them as normal boluses.