Merge pull request #1577 from MondayCoffee/fix_failToAddUserToSPOGroup

fix to #1553 if "_api/Web/SiteUsers" then the user is always added to the SiteUsers instead of the SPOGroup

src/sdk/PnP.Core/Model/Security/Internal/SharePointUser.cs

@@ -28,7 +28,7 @@ public SharePointUser()
                         LoginName
                     };
                     var jsonBody = JsonSerializer.Serialize(body);
-                    return new ApiCall("_api/Web/SiteUsers", ApiType.SPORest, jsonBody);
+                    return new ApiCall(entity.SharePointGet, ApiType.SPORest, jsonBody);
 
                 }).ConfigureAwait(false);
             };