Add incoming deprecation message for add-in docs

Author: VesaJuvonen

docs/sp-add-ins-modernize/sp-add-in-modernize.md

@@ -8,14 +8,14 @@ ms.localizationpriority: high
 
 # Modernization guidance for existing SharePoint add-in model implementations in Microsoft 365
 
-SharePoint add-in model was introduced as part of the SharePoint 2013 timeframe and it was also provided as an extensibility option for SharePoint Online (Microsoft 365). While SharePoint add-in model is currently still supported in the SharePoint Online, model and patterns and outdated and are not recommended to be used.
+SharePoint add-in model was introduced as part of the SharePoint 2013 timeframe and it was also provided as an extensibility option for SharePoint Online (Microsoft 365). While SharePoint add-in model is currently still supported in the SharePoint Online, model and patterns and outdated and aren't recommended to be used.
 
-Microsoft is looking into officially deprecating SharePoint add-in model in autumn 2023 - spring 2024 timeframe with clear communications on the detailed end-of-life schedule for related features.
+Microsoft is looking into officially deprecating SharePoint add-in model by end of 2023 in SharePoint Online, with clear communications on the detailed end-of-life schedule for related features.
 
 > [!IMPORTANT]
 > Deprecation means official statement that the feature is no longer being invested, but it's stil supported. End-of-life means that the feature will be discontinued and is no longer available for use.
 
-These upcoming changes will be impacting SharePoint add-in model and also authentication patterns using the classic [SharePoint Online hosted Microsoft Azure Access Control Service](https://learn.microsoft.com/sharepoint/dev/sp-add-ins/authorization-code-oauth-flow-for-sharepoint-add-ins) (ACS) authentication patterns, used with the provided hosted add-ins and potentially with other unattended services connecting to SharePoint Online.
+These upcoming changes are impacting SharePoint add-in model and also authentication patterns using the classic [SharePoint Online hosted Microsoft Azure Access Control Service](https://learn.microsoft.com/sharepoint/dev/sp-add-ins/authorization-code-oauth-flow-for-sharepoint-add-ins) (ACS) authentication patterns, used with the provided hosted add-ins and potentially with other unattended services connecting to SharePoint Online.
 
 ## Transformation technologies
 
@@ -55,4 +55,4 @@ Here's a list of all articles for the transformation guidance when moving away o
   * [From SharePoint Add-in model Workflow Apps to Microsoft Power Automate](./From-Workflow-Apps-to-Power-Automate.md)
   * [Publishing modern SharePoint applications on Microsoft AppSource](./Publishing-modern-SharePoint-apps-on-AppSource.md)
 
-If some essential guidance is not included, please open an issue at the [SharePoint developer documentation](https://aka.ms/spdev-issues) and we will try to help you as fast as possible with your specific question.
+If some essential guidance isn't included, open an issue at the [SharePoint developer documentation](https://aka.ms/spdev-issues) and we'll help you as fast as possible with your specific question.

docs/sp-add-ins/access-sharepoint-data-from-add-ins-using-the-cross-___domain-library.md

@@ -1,13 +1,15 @@
 ---
 title: Access SharePoint data from add-ins using the cross-___domain library
 description: Access data in a SharePoint website from your add-in by using the cross ___domain library in SharePoint.
-ms.date: 03/08/2023
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 
 # Access SharePoint data from add-ins using the cross-___domain library
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 When you build SharePoint Add-ins, you usually have to incorporate data from various sources. But for [security reasons](https://msdn.microsoft.com/library/cc709423.aspx), blocking mechanisms prevent communication with more than one ___domain at a time. These security mechanisms are implemented in most browsers, making it difficult or impossible to accomplish client-side calls across domains.
 
 When a user requests a page from your add-in ___domain, the client-side communication is bound only to that ___domain. Your add-in can issue client-side calls from the page only to other resources in the same ___domain. However, add-ins usually require resources from other domains, such as the SharePoint ___domain, to fulfill their scenarios. In the code on your page, you may try to issue a request to the SharePoint ___domain, which is blocked by the browser. You usually see an **Access is denied** error. The error doesn't imply that you don't have permissions to the requested resources but, most likely, you can't even issue a request to the mentioned resources.

docs/sp-add-ins/add-a-custom-content-type-to-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,12 +1,14 @@
 ---
 title: Add a custom content type to a SharePoint-hosted SharePoint Add-in
 description: Create a custom content type, run the add-in, and test it.
-ms.date: 11/22/2022
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 # Add a custom content type to a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the fourth in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-a-custom-page-and-style-to-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,12 +1,14 @@
 ---
 title: Add a custom page and style to a SharePoint-hosted SharePoint Add-in
 description: Add a custom page, add a style class to a stylesheet, and run and test the add-in.
-ms.date: 12/04/2017
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 # Add a custom page and style to a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the seventh in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-a-web-part-to-a-page-in-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,12 +1,14 @@
 ---
 title: Add a web part to a page in a SharePoint-hosted SharePoint Add-in
 description: Add a web part to a page, and run and test the add-in.
-ms.date: 07/25/2022
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 # Add a web part to a page in a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the fifth in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-a-workflow-to-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,11 +1,13 @@
 ---
 title: Add a workflow to a SharePoint-hosted SharePoint Add-in
 description: Add a workflow to an add-in, design the workflow, and run and test the add-in.
-ms.date: 10/21/2019
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 # Add a workflow to a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the sixth in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-custom-client-side-rendering-to-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,12 +1,14 @@
 ---
 title: Add custom client-side rendering to a SharePoint-hosted SharePoint Add-in
 description: Customize the rendering and validation of controls in add-in pages, create and register the JavaScript, and run and test the add-in.
-ms.date: 12/04/2017
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 # Add custom client-side rendering to a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the eighth in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-custom-columns-to-a-sharepoint-hosted-sharepoint-add-in.md

@@ -1,12 +1,14 @@
 ---
 title: Add custom columns to a SharePoint-hosted SharePoint Add-in
 description: Create custom column types, run the add-in, and test the columns.
-ms.date: 01/06/2021
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
 
 # Add custom columns to a SharePoint-hosted SharePoint Add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the third in a series of articles about the basics of developing SharePoint-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating SharePoint-hosted SharePoint Add-ins | Next steps](get-started-creating-sharepoint-hosted-sharepoint-add-ins.md#next-steps).
 
 > [!NOTE]

docs/sp-add-ins/add-first-run-logic-to-the-provider-hosted-add-in.md

@@ -1,13 +1,13 @@
 ---
 title: Add first-run logic to the provider-hosted add-in
 description: Include "first run" code in a provider-hosted SharePoint Add-in by creating the basic class for deploying components, adding the basic startup logic, and programmatically deploying a SharePoint list. 
-ms.date: 04/02/2021
+ms.date: 09/26/2023
 ms.localizationpriority: medium
 ---
-
-
 # Add first-run logic to the provider-hosted add-in
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 This is the eighth in a series of articles about the basics of developing provider-hosted SharePoint Add-ins. You should first be familiar with [SharePoint Add-ins](sharepoint-add-ins.md) and the previous articles in this series, which you can find at [Get started creating provider-hosted SharePoint Add-ins](get-started-creating-provider-hosted-sharepoint-add-ins.md#SP15createprovider_nextsteps). 
 
 > [!NOTE]

docs/sp-add-ins/add-in-authorization-policy-types-in-sharepoint.md

@@ -1,13 +1,13 @@
 ---
 title: Add-in authorization policy types in SharePoint
 description: Overview of add-in-only policy, user-only policy, and user+add-in policy, and guidelines for using the add-in-only policy.
-ms.date: 12/26/2017
+ms.date: 09/26/2023
 ms.localizationpriority: high
 ---
-
-
 # Add-in authorization policy types in SharePoint
 
+[!INCLUDE [sp-add-in-deprecation](../../includes/snippets/sp-add-in-deprecation.md)]
+
 Before reading this article, you should first be familiar with the articles [Add-in permissions in SharePoint](add-in-permissions-in-sharepoint.md) and [Context Token OAuth flow for SharePoint Add-ins](context-token-oauth-flow-for-sharepoint-add-ins.md).