Introduce an `AddNServiceBus` extension method on `IServiceCollection`

[ramonsmits]

Describe the suggested improvement

Currently NServiceBus only has a IHostBuilder extension method called UseNServiceBus. Most frameworks have a convenience Use.. method on the builder but also provide an Add.. extension method on IServiceCollection.

Usually when the framework only adds ServiceCollection entries use has an Add.. and sometimes for convenience a Use.. on the host builder.

• Serilog

  • Use (IHostBuilder): https://github.com/serilog/serilog-extensions-hosting/blob/v8.0.0/src/Serilog.Extensions.Hosting/SerilogHostBuilderExtensions.cs#L40
  • Add (IServiceCollection) : https://github.com/serilog/serilog-extensions-hosting/blob/v8.0.0/src/Serilog.Extensions.Hosting/SerilogServiceCollectionExtensions.cs#L56

• Hangfire

  • Add (IServiceCollection) : https://github.com/HangfireIO/Hangfire/blob/v1.8.14/src/Hangfire.NetCore/HangfireServiceCollectionExtensions.cs

• Hangfire dashboard

  • Use (IHostBuilder): https://github.com/HangfireIO/Hangfire/blob/v1.8.14/src/Hangfire.AspNetCore/HangfireApplicationBuilderExtensions.cs#L35

Describe the suggested solution

Follow conventions.

Currently this cannot work because our ServiceCollectionExtensions are private:

• https://github.com/Particular/NServiceBus.Extensions.Hosting/blob/3.0.0/src/NServiceBus.Extensions.Hosting/ServiceCollectionExtensions.cs#L7

Its because NServiceBus still uses its own logging abstraction.