Update an internal resource

Update internal resource details. Send the file either as a base64 data URI in file or as the URL that POST /api/core/private/v1alpha/files/ returned for private=true in fileUrl. Only a privately staged upload is accepted in fileUrl; a public upload URL is refused. The staged file must be an image (JPEG, PNG, SVG, WebP, GIF) or a PDF of at most 4 MB; it is copied into the resource’s protected storage and the staged copy is removed. file wins when both are sent: a well-formed fileUrl is then ignored without being checked (a malformed one is still refused). On update, fileUrl: null clears the file like file: null, and a fileUrl pointing at the resource’s current file is ignored. A resource needs either url or a file: send url: null with fileUrl to replace a link with a file.