Get a chart image

Renders a chart as a PNG image. Works for any chart the API key owner can access: charts on dashboards, charts created in chats, and insight charts. The image only includes data the API key owner is allowed to see. Pass chartVersionId to render a specific version; otherwise the latest version is rendered. API keys of members with the Viewer role can only render the latest version and get 409 for an older one. Rendered images are cached per chart version. IMAGE charts and dashboard header and text blocks (DASHBOARD_HEADER, DASHBOARD_TEXT) are never rendered as images; requesting one returns 422.