Release v19.23.1

Fixed

• The event serializer and the reactor side-effect handlers are always registered as scoped services, even when convention binding has already bound them as singletons. As singletons they captured the scoped event types registry (#4410)
• Reducers now log observation stream errors by kind: cancellation at Debug, a lost kernel connection at Warning while reconnecting, and any other failure at Error. Reconnect behavior is unchanged (#4374)