I found this that might be a pathway to your solution. But I don’t understand how to implement it.
https://book.cakephp.org/authentication/2/en/authenticators.html#url-checkers
I don’t know how other folks get up to speed, but I spend quite a bit of time tracking back to the core code (a process my IDE makes very easy). The doc blocks in the code often gives me insight on how to proceed. The API documentation provides the same thing but I find it hard to navigate. When I’m coding, I typically have all the method-hinting of the objects of interest and can quickly find and see exactly the docblocks and code of interest. In the case of the new Authentication, I’m not even sure where the API docs are.
It’s not unusual for me to drop debug-and-die commands in the core code to work my way to a solution.
Are these ideal approaches? Probably not.