fix: ensure clone method creates a deep clone

[Kyzegs]

Q	A
Branch?	4.0
Tickets	N/A
License	MIT
Doc PR	api-platform/docs#...

The CloneTrait clones only the top-level object. Updating nested object(s) on the clone will also update the nested object(s) in
the original object.

Imagine the following case with the current implementation:

/** @implements ProcessorInterface<AccountInput, AccountOutput> */
final class AccountUpdateProcessor implements ProcessorInterface
{
    /** @inheritDoc */
    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): ?AccountOutput
    {
        $data->getTwoFactorAuthentication()->getMethod(); // totp
        $context['previous_data']->getTwoFactorAuthentication()->getMethod(); // totp
        
        $context['previous_data']->getTwoFactorAuthentication()->setMethod('sms');
        
        // Any mutations on a nested object will reflect on the original object as the nested object uses the same reference as the original
        $data->getTwoFactorAuthentication()->getMethod(); // sms
        $context['previous_data']->getTwoFactorAuthentication()->getMethod(); // sms
    }
}

[Kyzegs]

I'll still have to add tests but I'd like to know if this is something that might be merged before I put any more time into it.

[soyuka]

can you explain your use case or where it fails?