I have been able to generate an Access Token from SharePoint however, I want to be able to update the Site Design using the REST API. Has anybody been able to call the site design API at all. I'm using the REST API call from Microsoft Docs.
RestRequest("/_api/Microsoft.Sharepoint.Utilities.WebTemplateExtensions.SiteScriptUtility.ApplySiteDesign", {siteDesignId: "614f9b28-3e85-4ec9-a961-5971ea086cca", "webUrl":"https://contoso.microsoft.com/sites/projectgo"});