Async cache wrong callback example

[torchello]

Hey! Seems like an example of a callback in async cache section is incorrect:

$cachedValue = $asyncCache->get('my_value', [CacheComputation::class, 'compute'])

It's not a valid callback as the compute method is not static in the example:

class CacheComputation
{
    public function compute(ItemInterface $item): string
    {
        ...
    }
}

Am I missing something or we should adjust the docs?

[torchello]

Actually, some info from this page could be added to the docs. Wdyt?
https://symfony.com/blog/new-in-symfony-5-2-async-cache-recomputing

[torchello]

Also, seems like

early_expiration_message_bus: messenger.default_bus

should be

early_expiration_message_bus: messenger.bus.default