Is there native support for some sort "tag groups"?

[lopis]

In my app I have two kinds of taggables: Products and Templates. Tags for each taggable have a different purpose so the two kinds don't even overlap. I don't understand the design decision to only have the resource_type on the Taggable side since "orphan" tags don't have a Tagable yet. I run into a few problems when I tried to add my own field to the Tag entity in Symfony. Is that suppose to be possible with no problems?