Formbase 0.15.0

Pairs with MorphDB 0.14.x. A batch of documents is accepted in one durable write. Breaking for code
that implements IRawStore or IIntakeService.

Added

• Accepting a batch in one durable write. FormbaseEngine.AcceptManyAsync(type, documents) takes
  documents and retirements of one form type (IntakeDocument.Accept, IntakeDocument.Retire) and stores
  them as one unit: when it returns all of them are durable, when it throws none is. Each accept on its own
  waits for its own commit — on SQLite, a sync to disk per document — so filling a store one document at a
  time is bound by that wait; a batch pays it once (10,000 documents into a SQLite file: about 13 times
  faster). On PostgreSQL a batch's inserts also travel together, a thousand to a round trip, so a database
  across a network is not waited on once per document. The batch's documents take consecutive watermarks in the order given. Idempotency keys work per
  document, so a batch cut off and sent again stores nothing twice; a key already holding another request
  refuses the whole batch with IdempotencyKeyReusedException, before anything is written.

Changed

• Breaking: IRawStore.AppendManyAsync(type, appends) is new — a raw-store adapter implements it,
  and must store the batch atomically, which is why there is no default implementation that appends one
  at a time. RawAppend.Distinct and RawAppend.EnsureRepeats carry the idempotency rule an adapter
  checks before writing. IIntakeService.AcceptManyAsync is new as well.