Add service definition for PsrAclCache

[mbabker]

Requires symfony/security-acl#72

This adds the service definition for the new Symfony\Component\Security\Acl\Domain\PsrAclCache class added to the component for use as a cache service.

[derrabus]

Adding the service definition alone won't be enough. The bundle would currently still alias the Doctrine cache as security.acl.cache, so the new cache service won't be used.

[mbabker]

The bundle would currently still alias the Doctrine cache as security.acl.cache, so the new cache service won't be used.

That alias is set from the cache.id config node (which defaults to null), it doesn't automatically map to the Doctrine cache implementation.

[derrabus]

Right, but the bundle does not integrate that new cache either.

How about a new option pool where I can specify one of the cache pools configured by FrameworkBundle that I want to be wired as ACL cache? Of course, we should throw an exception if the app specifies both options, id and pool.

[mbabker]

I've tweaked the bundle config to add the new option and adjusted everything else accordingly. Also added tests covering the cache service setup since none existed previously.

[wouterj]

Thank you @mbabker!