Move IServerVariablesFeature to Http.Features

[mderriey]

• Move IServerVariablesFeature to Http.Features and forward in Servers.IIS
• Create GetServerVariable in Http.Extensions
• Mark GetIISServerVariable obsolete in Servers.IIS

Addresses #10167

[Tratcher]

"You might need to regenerate the reference assemblies ... see docs/ReferenceAssemblies.md"
Microsoft.AspNetCore.Http.Features.netstandard2.0.cs

[mderriey]

Oh sorry about that, I thought I did for the projects which changed. I'll do it globally as I must have missed something.

Thanks.

[mderriey]

Errors in the latest builds

F:\workspace\_work\1\s\src\Servers\IIS\IIS\test\testassets\InProcessWebSite\Startup.cs(37,44): error CS0433: The type 'IServerVariablesFeature' exists in both 'Microsoft.AspNetCore.Http.Features, Version=3.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' and 'Microsoft.AspNetCore.Server.IIS, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' [F:\workspace\_work\1\s\src\Servers\IIS\IIS\test\testassets\InProcessForwardsCompatWebSite\InProcessForwardsCompatWebSite.csproj]
F:\workspace\_work\1\s\src\Servers\IIS\IIS\test\testassets\InProcessWebSite\Startup.cs(705,58): error CS0433: The type 'IServerVariablesFeature' exists in both 'Microsoft.AspNetCore.Http.Features, Version=3.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' and 'Microsoft.AspNetCore.Server.IIS, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' [F:\workspace\_work\1\s\src\Servers\IIS\IIS\test\testassets\InProcessForwardsCompatWebSite\InProcessForwardsCompatWebSite.csproj]
F:\workspace\_work\1\s\src\Servers\IIS\IIS\samples\NativeIISSample\Startup.cs(83,72): error CS0618: 'HttpContextExtensions.GetIISServerVariable(HttpContext, string)' is obsolete: 'This is obsolete and will be removed in a future version. Use GetServerVariable instead.' [F:\workspace\_work\1\s\src\Servers\IIS\IIS\samples\NativeIISSample\NativeIISSample.csproj]

I believe updating samples to use the new GetServerVariable method will fix the 3rd one.
I'm not too sure what needs to be done to fix the first two, though. I've never done type-forwarding before, so maybe I did it wrong?

Edit: Ah! I guess it might be there's 2 using directives and the compiler doesn't know which IServerVariablesFeature type to resolve to. Still a bit puzzled that there's 2.2 and 3.0 versions mixed up, but I'll see if being explicit fixes it

Edit #2: Found out why the versions being mixed up; it's because of InProcessForwardsCompatWebSite.

[Tratcher]

@jkotalik It's pretty strange that InProcessForwardsCompatWebSite mixes package versions like that. It should be all 2.2 or all 3.0.

[mderriey]

How dumb!

They both live in the same namespace so my attempt to differentiate one from the other via namespaces obviously didn't work.

[jkotalik]

@mderriey I'm going to take a stab at fixing the namespace resolution issue you are hitting.

[jkotalik]

Closing in favor of my new PR (as I couldn't push to your fork without cloning).