Release v19.83.0

Changed

• ReadModelScenario<T>: Given.ForEventSourceId(id).ReadModel(instance) now seeds the starting state for that read-model key. Events for the key apply on top of the seeded instance (setters, arithmetic and children), a reducer receives it as its current state for the key's first event, other keys start from the normal initial state, and a seeded key is returned by Instances and InstanceForEventSourceId even without events. Previously the seed was only returned by IReadModels.GetInstanceById and was ignored by the fold. Read models without a projection or reducer keep the lookup-only behavior. (#4846)
• ReadModelScenario<T>: seeding the same key twice throws ReadModelAlreadySeeded. (#4846)