Since the goal of reading events at the head of the event log is to satisfy a
subscription style interface, there is no point in allowing head polling with
no wait interval. The pagination case already bypasses long polling, so the
extra option is unneessary.
Set a minimum default long-polling interval for the head case.
Add a test for minimum delay.
Implement the basic cursor and eventlog types described in ADR 075. Handle
encoding and decoding as strings for compatibility with JSON.
- Add unit tests for the required order and synchronization properties.
- Add hooks for metrics, with one value to be expanded later.
- Update ADR 075 to match the specifics of the implementation so far.
