chore: refactoring some code to introduce a common base class for all api classes

src/Exceptions/PaymoApiException.cs

@@ -1,14 +0,0 @@
-using System;
-
-namespace Novaloop.PaymoApi.Exceptions
-{
-    public class PaymoApiException : Exception
-    {
-        public PaymoApiException(int statusCode, string message) : base($"[{statusCode}]: {message})")
-        {
-            StatusCode = statusCode;
-        }
-
-        public int StatusCode { get; }
-    }
-}