https://doc.photonengine.com/en-us/realtime/current/reference/custom-authentication

For example, I could login to Photon via GameSparks. From there, could capture Photon callbacks and such integrated into your SDK.

Would be super convenient :) Although I recently discovered you guys support realtime, too, so I'm not sure if this would conflict in your business model ~ 

Thank you very much for great tip

One way I've managed to do this is by using the undocumented Spark.systemCollection("player") then find my player document by id then check the authToken I got via photon authentication web hook.

Any update on validate the authToken?

Seems that this guy has a similar question (he wants to know how to validate the authToken):

https://support.gamesparks.net/support/discussions/topics/1000085416?page=1

Thanks - this helps a ton! I'm almost done, I just ran into 1 block:

I am providing an authentication token to prove they are currently authorized: how can I validate an AuthToken received from an AuthenticationResponse to prove they are already logged in in some form?

You can currently use Photon custom auth and callbacks with GameSparks, I tried this months ago and it works fine. These links will help you get going:

https://docs.gamesparks.com/tutorials/cloud-code-and-the-test-harness/using-custom-callback-urls.html

https://docs.gamesparks.com/tutorials/cloud-code-and-the-test-harness/implementing-external-http-callbacks.html