Stratara 4.4.6

A host on the Orleans execution model can now wait until a projection has applied what it committed, instead of
reading its read model and hoping the projection is through. Additive; no schema change and no migration.

Added

• IProjectionProgress (Stratara.Abstractions), registered by AddStrataraProjectionGrains().
  MarkAsync() returns a StoreMark that covers every entry committed at the time of the call, in every partition
  — on PostgreSQL also an entry that committed while another write was still open. WaitAsync(projection, mark, timeout), with the projection named by its type or its framework name, answers with a ProjectionWaitResult:
  Reached only once the projection has applied every entry the mark covers; otherwise, at the limit, Stalled,
  Suspended or TimedOut with the partitions behind; MarkNotApplicable at once for a mark taken under another
  reader or partition count. A rebuild or a full replay during a wait is waited through; an unknown projection is
  refused. See Read your own write in the projection guide.
• ICommittedPositionReader.CommittedHeadAsync, the highest position the store shows as committed. The default
  answers HeadAsync; the native PostgreSQL reader answers it without the horizon its head is held back to. A
  reader of your own that holds its head back overrides it.

Upgrade notes

• Adopt the wait once every silo runs this release: a silo of an earlier version does not answer it, and a wait
  whose partition lives there fails with the grain call's error.