Add the ability to use the logged on user credentials for proxy configuration

As for a feature request, we are having a bit of a tricky time using Chocolatey with our corporate proxy server. To start, our proxy server cannot be auto-detected by the .NET WebClient class for some reason. This requires us to configure the proxy server manually in Chocolatey. This is fine – we have to do this in our .NET code all the time. Also, our proxy server uses NTLM authentication but Chocolatey only supports user name and password authentication when configuring a proxy server manually. Our Active Directory user names and passwords do work from within the configuration for Chocolatey, but there are two problems with this. First, one user’s credentials are stored in the configuration for the computer instead of the tool using the current user’s credentials, if different. Second, when a user changes his/her AD password as required periodically by our network policy, he/she needs to remember to change it in Chocolatey as well.

What we would like to request is an option to use the “default network credentials” instead of a user name and password for proxy authentication when a proxy server is manually configured. And we would also like the same option added to the installation script. My suggestion for the installation script would be to have the variable $env:chocolateyProxyUseDefaultNetworkCredentials be understood by the script.

Start by locating Chocolatey's manually configured proxy handling and the installation script entry point; the issue does not name specific files or tests. Trace how username/password authentication is handled in both paths, then verify that an option for default network credentials and $env:chocolateyProxyUseDefaultNetworkCredentials works for each configuration path.

Written by the indexing model from the issue text.