[SITE-988] Consolidate WordPress Composer multisite config doc with the existing Multisite Configuration doc

source/content/guides/integrated-composer/06-ic-upstreams.md

@@ -3,8 +3,8 @@ title: Integrated Composer
 subtitle: Use an Upstream with Integrated Composer
 description: Learn how to use an Upstream with Integrated Composer.
 tags: [composer, workflow]
-contributors: [ari, edwardangert]
-reviewed: "2022-12-13"
+contributors: [ari, edwardangert, jazzsequence]
+reviewed: "2024-10-15"
 showtoc: true
 permalink: docs/guides/integrated-composer/ic-upstreams
 contenttype: [guide]
@@ -21,20 +21,45 @@ This section provides information on how to use an Upstream with Integrated Comp
 
 ## Upstreams
 
-An Upstream refers to the source code in Git that shares a Git history with "downstream" individual sites made from it. Upstreams includes the core code for [Drupal](https://github.com/pantheon-upstreams/drupal-composer-managed), [WordPress](https://github.com/pantheon-upstreams/wordpress-project), and some customizations for the Pantheon platform.
+An Upstream refers to the source code in Git that shares a Git history with "downstream" individual sites made from it. Upstreams includes the core code for [Drupal](https://github.com/pantheon-upstreams/drupal-composer-managed), [WordPress](https://github.com/pantheon-upstreams/wordpress-composer-managed), and some customizations for the Pantheon platform.
 
 ### Upstream and Site Structure
 
 <Partial file="ic-upstream-structure.md" />
 
 <Partial file="upstream-management-dependencies.md" />
 
+## Create Your Integrated Composer Custom Upstream
+
+Follow the steps in this section to create a custom upstream that uses Integrated Composer.
+
+1. Fork the Pantheon-maintained [WordPress (Composer Managed)](https://github.com/pantheon-upstreams/wordpress-composer-managed) or [Drupal Composer Managed](https://github.com/pantheon-upstreams/drupal-composer-managed) upstream repository.
+
+1. [Connect your repository](/guides/custom-upstream/create-custom-upstream#connect-repository-to-pantheon) to Pantheon.
+
+1. Update the **require** section of the root `/composer.json` file to match the name you chose in the preceding step.
+
+## Add and Remove Packages
+
+1. Use `composer require`in the `upstream-configuration` directory (or `composer upstream-require` if using `upstream-management`) to edit the upstream `composer.json` file.
+    - The WordPress (Composer Managed) repository places a theme in the upstream `composer.json` file. This works well for downstream sites that all use the same theme. You should remove themes from the upstream `composer.json` file if you do not intend to use the upstream to lock downstream sites into a particular theme. You cannot remove installed packages from downstream sites if the packages were included from the upstream site.
+
+## Maintain Your Integrated Composer Fork
+
+ There are some special considerations to keep in mind if you intend to make modifications to your upstream based on this repository.
+
+1. Increase the version number listed in the `upstream-configuration/composer.json` file each time you make edits.
+    - Composer checks the contents of the root `/composer.json` file for changes that should be pushed to your upstream configuration.
+
+1. Verify your changes to the `upstream-configuration/composer.json` file by running `composer install` or `composer update` in the `upstream-configuration` directory.
+    - Be careful not to rely on ["root-only" properties of composer.json](https://getcomposer.org/doc/04-schema.md).
+
 ## More Resources
 
 - [Custom Upstreams](/guides/custom-upstream)
-
 - [Autopilot for Custom Upstreams](/guides/autopilot-custom-upstream)
-
 - [Migrate a Custom Upstream to Drupal](/guides/drupal-hosted-createcustom)
-
 - [Pantheon YAML Configuration Files](/pantheon-yml)
+- [Best Practices for Maintaining Custom Upstreams](/guides/custom-upstream/maintain-custom-upstream)
+- [Composer Fundamentals and WebOps Workflows](/guides/composer)
+- [Create a Composer-managed WordPress Site with Bedrock](/guides/wordpress-composer/wordpress-composer-managed)

source/content/guides/multisite/03-config.md

@@ -132,6 +132,42 @@ Complete the steps below after spinning up a new WPMS site from the correct Cust
   /* That's all, stop editing! Happy Pressing. */
   ```
 
+## Setting up Multisite on WordPress (Composer Managed) sites
+
+The [Bedrock](https://roots.io/bedrock/)-based [WordPress (Composer Managed)](https://github.com/pantheon-systems/wordpress-composer-managed) upstream uses `Config::define()` and `config/application.php` instead of traditional `define()` statements in `wp-config.php`. You will not be able to use WP-CLI via Terminus to enable multisite as documented above in a standard multisite configuration. This section provides guidance on how to set up a WordPress Multisite using the WordPress (Composer Managed) upstream.
+
+1. Set the site's connection mode to Git:
+
+    ```bash{promptUser: user}
+    terminus connection:set <site>.dev git
+    ```
+2. Open the `config/application.php` file in your site's codebase and add the following line anywhere _above_ the `Config::apply();` line:
+
+	```php
+	Config::define( 'WP_ALLOW_MULTISITE', true );
+	```
+3. Visit your development site's WordPress admin and navigate to **Tools** > **Network Setup**.
+    ![Network Setup page](../../../images/wordpress-composer/04-multisite-network-setup.png)
+4. Choose **Sub-domains** or **Sub-directories** (depending on your needs), fill in the Network Title and Admin Email, and click **Install**.
+5. You will be given instructions to update your `config/application.php` file. Below where you added the `WP_ALLOW_MULTISITE` line, copy and paste the code provided. The `SUBDOMAIN_INSTALL` value will be `true` or `false` depending on the option you chose in the previous step. For example, if you chose subdirectories, your `config/application.php` file should look like this:
+
+	```php
+	Config::define( 'MULTISITE', true );
+	Config::define( 'SUBDOMAIN_INSTALL', false );
+	// Use PANTHEON_HOSTNAME if in a Pantheon environment, otherwise use HTTP_HOST.
+	Config::define( 'DOMAIN_CURRENT_SITE', defined( 'PANTHEON_HOSTNAME' ) ? PANTHEON_HOSTNAME : $_SERVER['HTTP_HOST'] );
+	Config::define( 'PATH_CURRENT_SITE', '/' );
+	Config::define( 'SITE_ID_CURRENT_SITE', 1 );
+	Config::define( 'BLOG_ID_CURRENT_SITE', 1 );
+	```
+6. Save your changes and commit them to your Git repository. WordPress will prompt you to log back in after you push the changes.
+7. Log into your site. When you log back into your WordPress admin dashboard, you will see a new **My Sites** menu item in the top left corner. This is where you can manage your network of sites. You now have a WordPress subdirectory multisite network set up on a WordPress (Composer Managed)-based upstream.
+	![My Sites](../../../images/wordpress-composer/04-multisite-my-sites.png)
+
+<Alert type="danger" title="Multisite Search and Replace with WordPress (Composer Managed)">
+Currently, the built-in dashboard [WordPress Multisite Search and Replace](/guides/multisite/search-replace/) does not support Composer-based WordPress multisites. To perform a search and replace on a WordPress (Composer Managed) multisite, you will need to use WP-CLI via Terminus manually. For more information, see our [WordPress Multisite Search and Replace](guides/multisite/workflows/#run-wp-cli-search-replace-manually) guide.
+</Alert>
+
 ## Develop the Multisite
 
 Congratulations on setting up your first WordPress Multisite. When you log in to the WordPress Dashboard, you'll see a **My Sites** menu item in the toolbar:
@@ -178,8 +214,8 @@ define( 'DOMAIN_CURRENT_SITE', PANTHEON_HOSTNAME );
 
 ## More Resources
 
-- [Environment-Specific Configuration for WordPress Sites](/guides/environment-configuration/environment-specific-config)
-
-- [WordPress Pantheon Cache Plugin Configuration](/guides/wordpress-configurations/wordpress-cache-plugin)
-
-- [WordPress with Composer on Pantheon](/guides/wordpress-composer)
+* [Environment-Specific Configuration for WordPress Sites](/guides/environment-configuration/environment-specific-config)
+* [WordPress Pantheon Cache Plugin Configuration](/guides/wordpress-configurations/wordpress-cache-plugin)
+* [WordPress with Composer on Pantheon](/guides/wordpress-composer)
+* [WordPress Multisite documentation](https://developer.wordpress.org/advanced-administration/multisite/)
+* [WordPress Multisite Domain Mapping](https://developer.wordpress.org/advanced-administration/multisite/domain-mapping/)