Async Function AddFieldToList(siteUrl As String, username As String, password As String, listName As String, fieldName As String, fieldType As String) As Task
Dim credentials As String = Convert.ToBase64String(Encoding.ASCII.GetBytes($"{username}:{password}"))
Using client As New HttpClient()
client.DefaultRequestHeaders.Authorization = New System.Net.Http.Headers.AuthenticationHeaderValue("Basic", credentials)