Flaky Postgres test: ProjectorTests.ProjectImportedBookingsToTable relies on a fixed 1s delay #599

ProjectorTests.ProjectImportedBookingsToTable (src/Postgres/test/Eventuous.Tests.Postgres/Projections/ProjectorTests.cs) produces 100 events, waits a fixed Task.Delay(1000), then reads each projected row. On a slow runner the projection hasn't caught up yet, ReadAsync returns false (unchecked), and reader["checkin_date"] throws:

InvalidOperationException: No resultset is currently being traversed
  at Npgsql.NpgsqlDataReader.ThrowIfNotInResult()
  at Eventuous.Tests.Postgres.Projections.ProjectorTests.ProjectImportedBookingsToTable(...) ProjectorTests.cs:40

This failed the 0.17.0 publish run (https://github.com/Eventuous/eventuous/actions/runs/36728898645, first attempt); a rerun of the same commit passed.

Fix:

• Replace the fixed delay with polling (with a timeout) until all expected rows exist, or until the subscription checkpoint reaches the last event.
• Assert that ReadAsync returned true so a missing row fails with a clear message instead of an Npgsql exception.