excluding certain slides while rendering

I often make slide decks (I still use Xaringan, but this will also be true when I move to Quarto for making my slides) that include several slides I do not want to include in a pdf handout.
So, I'll make an extensive set of slides and render those to html for my actual live presentation. But, when I share a pdf handout of the presentation afterwards, I usually want to exclude several slides (e.g., slides with copyrighted material, slides with the password for the wifi at a conference, slides that contain video, etc.).

It would be great if I could add a class to a slide that renderthis uses to skip it when building the pdf. For example, something like this:

---
class: not_handout

blabla content blabla
---

and then use: renderthis::to_pdf("slides.Rmd", skip = "not_handout")

Of course, if there already is some way to hack this, that would be great too.

Start at the renderthis::to_pdf("slides.Rmd", skip = "not_handout") entry point and trace how slide classes are handled during PDF rendering. Confirm that slides marked not_handout are omitted from the PDF while remaining available in the HTML presentation, and check the existing rendering behavior before defining the completion criteria.