[CSHARP] Bug - Nuget TLS1.2 Client Build fails

Description

Code generation of CSharp Client does not work anymore. Nuget Download requests tls1.2 protocol.
See:
https://devblogs.microsoft.com/nuget/deprecating-tls-1-0-and-1-1-on-nuget-org/

Exception calling "DownloadFile" with "2" argument(s): "The request was aborted: Could not create SSL/TLS secure 

channel."

At line:1 char:1

+ (new-object System.Net.WebClient).DownloadFile('https://dist.nuget.or ...

+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException

    + FullyQualifiedErrorId : WebException

'.\nuget.exe' is not recognized as an internal or external command,
operable program or batch file.

Swagger declaration file content or url

modules/swagger-codegen/src/main/resources/csharp/compile.mustache

Line 13:
if not exist ".\nuget.exe" powershell -Command "(new-object System.Net.WebClient).DownloadFile('https://dist.nuget.org/win-x86-commandline/latest/nuget.exe', '.\nuget.exe')"
.\nuget.exe install src\{{packageName}}\packages.config -o packages

Suggest a fix/enhancement

Line 13: Replace with protocol settings.

if not exist ".\nuget.exe" powershell -Command "[System.Net.ServicePointManager]::SecurityProtocol+=[System.Net.SecurityProtocolType]::Tls12; (new-object System.Net.WebClient).DownloadFile('https://dist.nuget.org/win-x86-commandline/latest/nuget.exe', '.\nuget.exe')"
.\nuget.exe install src\{{packageName}}\packages.config -o packages

Inspect modules/swagger-codegen/src/main/resources/csharp/compile.mustache, especially line 13 and the surrounding NuGet download commands. Verify the generated C# client build path and confirm that the NuGet download and package installation complete successfully when TLS 1.2 is required.