Startup.cs

public class Startup
{
    ...
    public void ConfigureServices(IServiceCollection services)
    {
        ...
        // Overwrite the default ApiContentResponseBuilder to resolve partial layouts
        services.AddSingleton<IApiContentResponseBuilder, ExtendedApiContentResponseBuilder>();
        services.AddSingleton<IComponentResolver, HeaderResolver>();
        services.AddSingleton<IComponentResolver, FooterResolver>();
    }
}