get-principal-token.ps1

$Fields = @{
  grant_type    = "client_credentials"
  client_id     = "<service-principal-id>"
  resource      = "<resource-id-to-auth-for-or-url>"
  client_secret = "<service-principal-secret>"
};
$response = Invoke-RestMethod `
    -Uri "https://login.microsoftonline.com/<azure-tenant-id>/oauth2/token" `
    -ContentType "application/x-www-form-urlencoded" `
    -Method POST `
    -Body $Fields;
 
Write-Output $tokenResponse.access_token