I am attempting to deliver a headless solution for a large multi-site installation using Umbraco 12 and the Delivery API but I am finding it quite limiting (possibly intentionally so?) at the moment and it feels like we might have to end up implementing our own API after all. Let's take, for example, a document that is a Site Map page which on a standard site with an Umbraco Front End would render a site map on the page. It doesn't store this site map data in the document properties (for obvious reasons) and so is not returned as part of the Delivery API response for that document. We still want the Site Map document as there are other properties on there relevant to the presentation of the content but we need to inject the contents of the sitemap into the response. Any ideas on how to achieve this without implementing a custom API separate to the Delivery API and forcing the consumers of the API to work with two different API's to get the content they need?