Add appSessionID to PaywallEventsManager

[vegaro]

Added an appSessionID that can be shared between all events. Since at the moment session_identifier in the paywalls represent the paywall session, not the whole app session.

I just added the generation, a reset functionality and a fallback for now

[vegaro]

I am unsure about this, but paywallEventsManager is an actor

[fire-at-will]

Yeah, since paywallEventsManager is an actor, this call has to be async. Ideally, the login function itself would be async and we wouldn't have to spawn a child task here, but that's a whole other refactor 🤷‍♂️

I think the biggest risk is that login() completes before resetAppSessionID() is done, and then some event gets emitted without the new app session ID. I don't think it's likely, but if we want to be safe here, we could consider calling the completion handler in the Task after resetAppSessionID completes.

[fire-at-will]

It looks like we're generating an app session ID when login/logout are called, but does one get created if the developer doesn't call those functions?

I don't have the full context on this feature, so it might not be necessary, but just wanted to make sure!

[vegaro]

@fire-at-will Yes, in the init of PaywallEventsManager https://github.com/RevenueCat/purchases-ios/pull/4482/files#diff-dcba7f0e5ca516087d45ef4b0bcd031d91ad329aa90d8e86b0928e2484ad07d3R48. Maybe it's not clear enough?

Btw, I am happy to change the approach :)

I tested that old Paywall Events would have an associated app session ID (on the SDK only not in the event sent yet)