add feature flag for organization user notification banner

Author: nick-livefront

src/Core/Constants.cs

@@ -264,6 +264,7 @@ public static class FeatureFlagKeys
     public const string PM29438_DialogWithExtensionPromptAccountAge = "pm-29438-dialog-with-extension-prompt-account-age";
     public const string PM31039_ItemActionInExtension = "pm-31039-item-action-in-extension";
     public const string PM29437_WelcomeDialogNoExtPrompt = "pm-29437-welcome-dialog-no-ext-prompt";
+    public const string PM31948_OrgUserNotificationBanner = "pm-31948-org-user-notification-banner";
 
     /* Innovation Team */
     public const string ArchiveVaultItems = "pm-19148-innovation-archive";