Add AuthCodeTokenExchangeFailed event to catch failures exchanging code for tokens

[bryanapellanes-okta]

After extensive investigation into this issue (https://github.com/okta/okta-oidc-xamarin/issues/44) I've determined the root cause. The root certificate authority for the custom domain is not trusted by the android device so, after authentication completes, the Sdk attempts to exchange the authentication code for tokens but the call fails because the root CA is not trusted. See this line of code, https://github.com/okta/okta-oidc-xamarin/blob/release-v3.0.0-dev/Okta.Xamarin/Okta.Xamarin/OidcClient.cs#L489

This issue cannot be corrected using only Xamarin tools, related Xamarin issue here: https://github.com/xamarin/xamarin-android/issues/2176 See subsequent comment below

In order to trust the CA one must use one of the options described here: https://developer.android.com/training/articles/security-config

However, there is no easy intuitive way to add the xml attribute android:networkSecruityConfig="@xml/network_security_config" to the application element of the AndroidManifest.xml file. To accomplish this, one must first build the Xamarin Android project, then navigate in the filesystem to the location the Xamarin build tools place temporary files and manually edit the AndroidManifest.xml file directly. In my case the build output went to ./obj/Debug/110/ See subsequent comment below

I will modify the Okta Sdk to bring awareness to our developers when this issue arises, by adding an AuthCodeTokenExchangeFailed event.

Originally posted by @bryanapellanes-okta in https://github.com/okta/okta-oidc-xamarin/issues/44#issuecomment-921959099

[bryanapellanes-okta]

Correction to the above; apparently adding the android:networkSecurityConfig="@xml/network_security_config" attribute to the application manifest is possible by editing the AndroidManifest.xml file that exists in the Properties folder of your Xamarin Android project.

[bryanapellanes-okta]

This is fixed in release v3