\OCA\DAV\CardDAV\ImageExportPlugin allows serving arbitrary data with user-defined or empty mimetype

The SabreDAV plugin `\OCA\DAV\CardDAV\ImageExportPlugin` is used for displaying pictures of a VCF. It registers on a GET request on a CardDAV element and acts when the query parameter `photo` is sent.

/**
 * Intercepts GET requests on addressbook urls ending with ?photo.
 *
 * @param RequestInterface $request
 * @param ResponseInterface $response
 * @return bool|void
 */
function httpGet(RequestInterface $request, ResponseInterface $response) {

	$queryParams = $request->getQueryParameters(); …