How to render (and store) an excerpt for PlaceholderFields?

[lunanoko]

Hi,

I seem unable to find any concrete information about rendering an excerpt for my custom model's PlaceholderFields. Is there any recommended way to do this? I hoped there would be an API for doing so, but unfortunately I cannot find such a thing.

At the moment all I can find is the ContentRenderer class in the cms.plugin_rendering module. Then I'd first need to instantiate a ContentRenderer with a Request, and then call its render_placeholder() method which needs a Context. Surely there must be an easier way?