Release v0.8.0

Added

• Projections can build children of a derived-type family: a children collection of an interface with exactly one registered derivative uses that concrete type for its fields, key, parent key and mapping tags, and writes _derivedTypeId on every child From, so the family codec reads the child back even when the kernel adds it from a keyed update after removal or before creation; the C# client stamps only the creating event. The fluent projections.Children accepts the same family with the derivative's builder, and a derivative's key, no-auto and not-projected tags do not turn another read model that holds the family as a whole property into a projection. See project derived children. (#27)

Changed

• Compiling a projection now fails with a located declaration error when a derived children collection has no or several registered derivatives, when its discriminator cannot be written as a kernel literal, when a global mapping targets _derivedTypeId, or when a derivative declares projection mappings outside a children collection of its family, including nested interface fields. The C# client instead writes children without a discriminator or drops those declarations.