RiverSource[T] should provide a continuous stream of data, never terminating as it does now.
Ideally we would still provide a batch mode of operation too.
- unbounded - the
paging iterator should poll the stream on the interval specified in the meta.
- bounded - the
paging iterator should read until a given point in event time, then terminate. All streams should end at the same (event) time - "now" by default.