Add AggregateNotFoundError for commands/events on non-existent aggregates

[Copilot]

The framework raised AggregateAlreadyExistsError when create commands/events targeted existing aggregates, but had no equivalent error for non-create operations on non-existent aggregates.

Changes

• Added AggregateNotFoundErrorEvent in main/shared/src/main/java/org/elasticsoftware/akces/errors/

  • Mirrors AggregateAlreadyExistsErrorEvent structure with aggregateId and aggregateName fields

• Updated KafkaAggregateRuntime

  • Added aggregateNotFound() method to emit error event with generation -1
  • Modified handleCommand() and handleEvent() to check for null state and call aggregateNotFound()

• Updated AggregateBeanFactoryPostProcessor

  • Added AggregateNotFoundError to COMMAND_HANDLER_SYSTEM_ERRORS list
  • Created EVENT_HANDLER_SYSTEM_ERRORS list with AggregateNotFoundError
  • Updated generateEventHandlerErrorEventTypes() to use new system error list

Behavior

Non-create commands and external events targeting non-existent aggregates now emit AggregateNotFoundError instead of failing silently or throwing exceptions:

// Attempting to credit non-existent wallet
CreditWalletCommand command = new CreditWalletCommand(nonExistentId, "USD", amount);
List<DomainEvent> result = akcesClient.send("TENANT", command).get();
// Returns: [AggregateNotFoundErrorEvent]

Original prompt

On KafkaAggregateRuntime.java, In KafkaAggregateRuntime.handleCommandRecord we currently raise an AggregateAlreadyExistsError however we don't do the same when the Aggregate does not exist. Add support for an AggregateNotFoundError to be raised in a similar fashion. Don't forget to add it the system errors as well in AggregateBeanFactoryPostProcessor

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