Equivalent of docs: { source: { state: "open" }} in SB7

[split lynx]

After migrating to SB7 I no longer see the source code of a canvas element/story in a docs page auto-expanded. I have been using the following in preview.js to make "Show code" auto-expanded for all stories:

docs: {
  source: {
    state: "open"
  }
}

but on SB7 all of the source blocks are closed by default. They're also closed by default when I try to configure them per story:

[rotund grove]

parameters.docs.canvas.sourceState = 'shown'

(Finalizing the updated docs now!)