Allow encapsulation of AggregateRepository

[BreiteSeite]

The only way currently to use the AggregateRepositoryFactory is to create a class that inherits from AggregateRepository.

This has multiple drawbacks. Two of them are:

• My repositories suddenly exposes more public functions than i like (for example getAggregateRoot).
• it it makes testing more difficult

Technical it's possible to create an instance of AggregateRepository (no subclass of it) and put it as dependency into my repository and use it (as AggregateRepository::saveAggregateRoot() and AggregateRepository::getAggregateRoot() are public functions).

The only things thats prevent me from doing it is this check in AggregateRepositoryFactory:

if (! \is_subclass_of($repositoryClass, AggregateRepository::class)) {
    throw ConfigurationException::configurationError(\sprintf(
        'Repository class %s must be a sub class of %s',
        $repositoryClass,
        AggregateRepository::class
    ));
 }

I think the check here should use is_a(), to allow me to create not only children of AggregateRepositories, but also direct instances of AggregateRepository.

If you can confirm that it is a valid approach to create the factory without creating subclasses of it, i could create a pull request for it.

[prolic]

This library is meant as a blueprint for you to create your own implementation. Your domain model shouldn't have dependencies to a framework or library.