Schema on how to store the data in object store:

{
    "name": "Wikipedia",
    "identifier": "simplewiki",
    "url": "https://simple.wikipedia.org",
    "version": "e4d909c290d0fb1ca068ffaddf22cbd0",
    "dateModified":"2021-05-12T00:59:14Z",
    "inLanguage": {
      "name": "Simple English",
      "identifier": "simplewiki"
    },
    "size": {
      "value": 321,
      "unitText": "MB"
    }
  }

Name of the object in the store should be something like {project_identifier}_{namespace_identifier}.json.

I heard a rumour that this is live someplace, but I don't see it in the api results: https://api.wikimediaenterprise.org/v1/docs/index.html#/projects/v1_projects_list
Where should I be looking?

It's not fully live yet, but will be pretty soon. Testing this things out a bit and will give a info where to grab them as soon as it's out.