Match the shipped InboundDatabaseHelper throughout the implementation plan:
QuerySingle->QuerySingleAsync (and Query->QueryAsync) — async signatures
(async Task<T?>), awaited async ADO.NET (ExecuteScalarAsync/ExecuteReaderAsync/
ReadAsync with the deadline token), async Task test methods with await, and the
architecture/step/acceptance prose + pseudocode now call
await Database.QuerySingleAsync<T>(...). Sibling fix to the design-doc correction.
Joseph Doherty
33da8c797c