[flutter_appauth] remove idTokenHint assert

[clintpurser]

Hi @MaikuB

I am wondering if there is a specific reason for this assert?

Currently we want to only supply our postLogoutRedirectUrl but not the idTokenHint for logging out in our app. We tried using the additionalParameters field to supply only the post_logout_redirect_uri, but that causes fatal exception in android.

Would be nice to remove this assert, unless there is a reason with OpenID why we'd want to enforce it like this.

Let me know! Thank you!

[MaikuB]

Hi @clintpurser, it's been a while so I don't remember the exact reasoning. I believe the goal was encouraging developers to providing all details or nothing at all. Typically both are given as giving both is indicates the app is providing details on who should be logged out and where the IdP should go to upon a successful logout. These are assertions though so shouldn't be impacting release builds