0.12.2

Fixed

• An observation could not land. A commit of an instance as it stands with one more event at its current revision — something seen about it, not a change to it — was lost by three of the four providers: SqliteStore and PostgresStore keyed events by (revision, position in the decision), so the second observation at one revision failed the primary key and the caller was told the store was broken; FileStore appended only events past the highest revision it had reached, so an observation was dropped with nothing said. The position now continues from what the log holds at that revision, the file log deduplicates by the event itself, and the provider conformance suite has a tenth case — two observations at one revision must both land, in order — so no provider can pass the suite without them.