I am trying to setup S2S Callbacks to check for a survey completion for Pollfish (https://www.pollfish.com/docs/s2s). 1. My question is that how do these callbacks work? 2. Do I have to have my own server to verify these callbacks, if so how do I set one up using Firebase if in any way possible? 3. Do I get to see the url callback in my debug console after a survey completion?
I have never used PHP before, so I don't have any knowledge about this or how to go about it using my Flutter app.