The using directive for 'System' appeared previously in this namespace

The using directive for 'System.ComponentModel' appeared previously in this namespace

Possible null reference assignment.

Possible null reference assignment.

Possible null reference assignment.

Nullability of reference types in type of parameter 'additionalAuthenticationContext' of 'Task<string> TokenProvider.GetAuthorizationTokenAsync(Uri uri, Dictionary<string, object> additionalAuthenticationContext = null, CancellationToken cancellationToken = default(CancellationToken))' doesn't match implicitly implemented member 'Task<string> IAccessTokenProvider.GetAuthorizationTokenAsync(Uri uri, Dictionary<string, object>? additionalAuthenticationContext = null, CancellationToken cancellationToken = default(CancellationToken))' (possibly because of nullability attributes).

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.