Replace Global Variables with SessionState

[jeffpatton1971]

Instead of exposing information via $Global, we should be placing sensitive information in the sessionState.

https://docs.microsoft.com/en-us/dotnet/api/system.management.automation.sessionstate

current

Set-Variable -Name azDevOpsHeader -Value $azDevOpsHeader -Scope Global

proposed

$PSCmdlet.SessionState.PSVariable.Set('azDevOpsHeader',$azDevOpsHeader)

There is potential to set scope on these to make them private so they are only accessible within the module.