So following the example I created a Blazor WASM front end with a .Net Web Api back end. In addition I created a custom claim that adds the groups I have add the user to. This works fine on the front end but when passed backed to the .Net Core Web API side of things the custom claim for the groups is gone.
This is the code I used.
builder.Services.AddHttpClient("KeeperLife.UI.ServerAPI", client => client.BaseAddress = new Uri(builder.HostEnvironment.BaseAddress))
.AddHttpMessageHandler<BaseAddressAuthorizationMessageHandler>();
// Supply HttpClient instances that include access tokens when making requests to the server project
builder.Services.AddScoped(sp => sp.GetRequiredService<IHttpClientFactory>().CreateClient("KeeperLife.UI.ServerAPI"));