Merge of #1658. Thanks @kola-tm

Author: bjansen

src/sdk/CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ### Added
 
 - Support for reading Alerts [jansenbe - Bert Jansen]
+- Allow optional configuration of used SharePointRestClient and MicrosoftGraphClient #1659 [kola-tm]
 
 ### Changed
 

src/sdk/PnP.Core.Test/Base/SetupTests.cs

@@ -93,7 +93,7 @@ public void PnPContextFactory()
             Assert.ThrowsException<ArgumentNullException>(() =>
             {
                 ServiceCollection services = new ServiceCollection();
-                services.AddPnPContextFactory(null);
+                services.AddPnPContextFactory(null, null, null);
             });
         }
     }