Integrate hook to pre-process the frontend rendering
Imagine the situation that the frontend rendering process has a special strategy to deliver content. For example some stored data could be used to serve the request directly but in some situations that shall not be allowed (e.g. when a frontend user is logged in) and then the regular TYPO3 rendering should be executed.
Currently there is no early hook in index_ts.php that can handle this scenario.
(issue imported from #M10869)