My goal is to be able to recreate this chart on an external dashboard system:

Have read through the latest API docs here, and tested it out on my own.
GET /rest/api/2/version/{id}/unresolvedIssueCount is the closest endpoint that returns a value for issuesUnresolvedCount and total issuesCount, (which I can use to deduce the doneIssueCount) but I don't get a value for issuesInProgressCount anywhere. I don't see any of the version endpoints that returns those values.
So my question is:
Do I simply have to write a GET /issues query to see the count? or am I missing something.