Add enum support

[samdark]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	?

enum PostStatus: string
{
    case DRAFT = 'draft';
    case PUBLISHED = 'published';
}

class Post
{

    public function __construct(
        #[\Yiisoft\Validator\Rule\In(PostStatus::class)]
        private string $status
    )
    {
    }
}

[samdark]

Consider #[EnumValue(PostStatus::class)] instead of #In(PostStatus::class)].

[samdark]

Also need to cover new code with tests.

[samdark]

Likely need an ability to verify against names and non-backed enums.

[samdark]

#[InEnum(PostStatus::class)]. Could also set names: true to force using names for backed enums. For non-backend ones, names will be used.