Simplify registration of ServerSideTokenStore

[josephdecock]

The AddBlazorServerAccessTokenManagement extension method in Duende.AccessTokenManagement registers an IUserTokenStore implementation as a singleton. This doesn't work in the Duende.Bff.Blazor, because its implementation of the store (ServerSideTokenStore) has a dependency on the AuthenticationStateProvider, which can't be resolved in a singleton context.

Right now, we have this workaround:

       builder.Services.AddOpenIdConnectAccessTokenManagement()
            .AddBlazorServerAccessTokenManagement<ServerSideTokenStore>();

        var removeThis = builder.Services.First(d => d.ImplementationType == typeof(ServerSideTokenStore));
        builder.Services.Remove(removeThis);
        builder.Services.AddScoped<IUserTokenStore, ServerSideTokenStore>();

Instead, we should fix AccessTokenManagement to register the type parameter as Scoped. I think it would be ok to release that as a patch release, as this is pretty clearly a bug.