New returns a new checkpointer from a base offset, which is the value returned when no checkpoints have yet been resolved.

ErrOutOfSync is returned when an offset to be tracked is less than or equal to the current highest tracked offset.

ErrResolvedOffsetNotTracked is returned when an offset to be resolved has not been tracked (or was already resolved).

Type receives an ordered feed of integer based offsets being tracked, and an unordered feed of integer based offsets that are resolved, and is able to return the highest offset currently able to be committed such that an unresolved offset is never committed.