feat: allow generic class names in interface inferring

[romm]

It can sometimes be useful for an inferred interface implementation to be a generic class. To do so, it is not possible to use the class-string return type, because by nature a class-string cannot be generic.

To do so, a workaround is implemented: instead of returning a class-string, the callback can return a string value containing the signature of the generic class.

namespace My\App;

interface ApiResponse {}

/**
 * @template T
 */
final readonly class SuccessResponse implements ApiResponse
{
    /** @var T */
    public mixed $data;
}

final readonly class User
{
    public string $name;
    public string $email;
}

final readonly class Product
{
    public string $name;
    public float $price;
}

$mapper = (new \CuyZ\Valinor\MapperBuilder())
    ->infer(
        ApiResponse::class,
        /**
         * @return '\My\App\SuccessResponse<\My\App\User>'
         *        |'\My\App\SuccessResponse<\My\App\Product>'
         */
        static fn (string $type): string => match($type) {
            'user' => '\My\App\SuccessResponse<\My\App\User>',
            'product' => '\My\App\SuccessResponse<\My\App\Product>',
            default => throw new \DomainException("Unhandled `$type`."),
        }
    )
    ->mapper();

$userResponse = $mapper->map(ApiResponse::class, [
    'type' => 'user', // Will return a `SuccessResponse<User>`
    'name' => 'John Doe',
    'email' => '[email protected]',
]);

assert($userResponse instanceof SuccessResponse);
assert($userResponse->data instanceof User);

$productResponse = $mapper->map(ApiResponse::class, [
    'type' => 'product', // Will return a `SuccessResponse<Product>`
    'name' => 'Laptop',
    'price' => 1337.42,
]);

assert($productResponse instanceof SuccessResponse);
assert($productResponse->data instanceof Product);

Fixes #270