Configuration of .NET 7+ using HostApplicationBuilder

[stevejgordon]

Since .NET 7, the preferred use of the generic host has been first to create a HostApplicationBuilder, which implements IHostApplicationBuilder, from the static method on the Host type. e.g.

HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
builder.Services.AddHostedService<Worker>();
IHost host = builder.Build();

We do not currently provide extension methods to support the registration of the APM agent.

It's possible to work around this by manually creating an APM instance (although that won't include hooks such as integrating with the logging extensions) or switching to the older (no longer preferred) Host.CreateDefaultBuilder style code instead.

Implementing the current behaviour is complicated since the new flow doesn't expose an intermediate IServiceProvider.

A further scenario we should consider is enabling APM in .NET Maui apps, which use the MauiAppBuilder.

We should likely provide an IServiceCollection extension method to enable APM.