Command bus upgrade to 9

[ossigeno]

Previously the handle signature was
public function handle(CommandInterface $command)

now is
public function handle(CommandInterface $command) : mixed

What is the handle expected to return? There is nothing mentioned here:
https://makoframework.com/docs/9.0/learn-more:command-bus

[freost]

It does say that it can have a return value:

The CommandHandlerInterface::handle() method can return data that can be used to handle successes and errors.

But I agree that enforcing mixed when you're not returning anything looks bad so I'll remove the return type from the interfaces.