Generics for repositories and repository interfaces

[dkarlovi]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	yes

Doctrine's \Doctrine\Persistence\ObjectRepository supports generics. Since CS interfaces extend it, it would make sense to denote they're generic too.

For example, it would mean adding

/**
 * @template T
 *
 * @extends ObjectRepository<T>
 */
interface CoreShop\Component\Resource\Repository\RepositoryInterface extends ObjectRepository

and then

/** 
 * @template T of PaymentProviderInterface
 *
 * @extends RepositoryInterface<T>
 */
interface PaymentProviderRepositoryInterface extends RepositoryInterface

This would also make many of the types inferred by default by Psalm / PHPStan and many PHPDoc blocks could be removed.

[dkarlovi]

Additional example: https://psalm.dev/r/11594ec601