Adding a option to keep the login credentials as a PSCredential object when using Add-PodeAuthWindowsAd

[TheBakaBandit]

Description

Sometimes we want to keep the login credentials of WindowsAD users in order to run some scripts as that user.

Suggestion

We can add a switch -KeepCredential to the Add-PodeAuthWindowsAd function, which stores the Users details as a PSCredential object in $WebEvent.Auth.User.Credential