Namespace .AspNetCore.Hosting vs .Extensions.Hosting : <p>In my ASP.NET Core 2.0 project, I've been using IHostingEnvironment and IApplicationLifetime from Microsoft.Extensions.Hosting namespace.</p>

<p>In ASP.NET Core 2.1, these interfaces seem to be in both Microsoft.AspNetCore.Hosting and Microsoft.Extensions.Hosting namespaces. What is the difference and which namespace should I be using?</p>

<p>FYI, I am also using BackgroundService class which is now (Core 2.1) in Microsoft.Extensions.Hosting namespace.</p>
