fix task name

Author: JohnDuprey

Modules/CIPPCore/Public/Entrypoints/HTTP Functions/Identity/Administration/Users/Invoke-AddUser.ps1

@@ -15,9 +15,10 @@ function Invoke-AddUser {
     $UserObj = $Request.Body
 
     if ($UserObj.Scheduled.Enabled) {
+        $Username = $UserObj.username ?? $UserObj.mailNickname
         $TaskBody = [pscustomobject]@{
             TenantFilter  = $UserObj.tenantFilter
-            Name          = "New user creation: $($UserObj.mailNickname)@$($UserObj.PrimDomain.value)"
+            Name          = "New user creation: $($Username)@$($UserObj.PrimDomain.value)"
             Command       = @{
                 value = 'New-CIPPUserTask'
                 label = 'New-CIPPUserTask'