ClientCertificates does not accept an environment variable

[stevestock]

NuGet Product(s) Involved

NuGet.exe

The Elevator Pitch

This ClientCertificates feature does not take an environment variable

example:

<configuration>
    ...
    <packageSources>
        <add key="Contoso" value="https://contoso.com/packages/" />
    </packageSources>
    ...
    <clientCertificates>	
        <storeCert packageSource="Contoso"
                   storeLocation="currentUser"
                   storeName="my"
                   findBy="thumbprint" 
                   findValue="%THUMBPRINT_VARIABLE%" />
    </clientCertificates>
...
</configuration>

currently the findValue only works if directly set to the thumbprint string

Additional Context and Details

No response

[nkolev92]

Environment variable transforms are not supported in every setting. https://github.com/NuGet/NuGet.Client/blob/72ab0e05562bc8e19db1ce0c2630a80e0bd3ca28/src/NuGet.Core/NuGet.Configuration/Settings/Settings.cs#L670-L677

They're only supported in add and source items, so this would is a new feature request.
The docs might need to be improved to call that out though.