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 ~ 

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.

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

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?

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

Thank you very much for great tip

Any update on validate the authToken?