Make the doctrine/common dependency optional

[derrabus]

Doctrine ORM has moved away from the Doctrine Common proxy implementation. Yet, this package still forces the installation of doctrine/common.

The only class that we need from doctrine/common is ClassUtils which can resolve proxy class names. However, if doctrine/common is not installed, we can be sure that we won't encounter any Common proxies and fall back to get_class(). This class introduces a new utility method that does exactly that.

[phansys]

Thanks @derrabus!

IIUC, I see other uses that also need to be replaced. By instance:

DoctrineExtensions/src/Translatable/Mapping/Event/Adapter/ORM.php

Line 12 in 389be08

use Doctrine\Common\Proxy\Proxy;

[derrabus]

DoctrineExtensions/src/Translatable/Mapping/Event/Adapter/ORM.php

Line 12 in 389be08

use Doctrine\Common\Proxy\Proxy;

That particular usage is safe. The Proxy interface is used in an instanceof check which is safe to perform on an undefined interface.

[derrabus]

That being said, $x instanceof Proxy is not a safe way to check if a given object is a proxy because it misses proxies that have been created with a different strategy (e.g. lazy ghosts). But fixing that is a bit out of scope for my PR.