Having the handler wrapped with a "context manager" allow us to some magical stuff  🪄

Example: transactional context

1. Api controller send (sendSync) a submitOrderCommand on the local command bus
2. A fresh context is initialised (is passed to the handler) and the transaction BEGIN
3. The SubmitOrderCommandHandler run some business logic and persist the aggregate (or whatever) using passed transaction (something like await this.repo.save(aggregate, context.transaction); )
4. The SubmitOrderCommandHandler publish an OrderSubmittedEvent on a local event bus (using publishAndWaitForHandlers). The event is local, so in the payload, in addition to the business data, the context of the command is also put
5. The OrderSubmittedEventHandler will probably send another command (something like await this.commandBus.send(command, payload.context);
6. The context manager sees that there is a transaction and passes it to the handler without creating another one
7. Since everything is awaited, when the last handler in the chain slowly resolves everyone and when the first one resolves, the transaction is committed (or rollback if the last handler reject)