Get access token from Azure AD OAuth 2.0 endpoint

GetToken.ps1

Function GetToken
{
    param(
        [String] $authority = "https://login.microsoftonline.com/lab09.onmicrosoft.com/oauth2/token",
        [String] $clientId = "<your_client_id_here>",
        [String] $clientSecret = "<client_secret>",
        [String] $resourceId = "https%3a%2f%2fgraph.windows.net"
    )

    $body = "grant_type=client_credentials&resource=$($resourceId)&client_id=$($clientId)&client_secret=$($clientSecret)"
    $res = Invoke-WebRequest -Uri $authority -Body $body -Method Post
    $authResult = $res.Content | ConvertFrom-Json
    return $authResult.access_token
}