[docs] UPDATING: document upgrade to NC 25.0.5

Along with the newly supported dd.conf variables and the docker image
rework.

UPDATING.md

@@ -24,6 +24,41 @@ little to no impact.
 
 ## 2023
 
+### 2023-03 - Nextcloud 25.0.5 + NC Docker rework
+
+Update version to 25.0.5 and rework its docker image.
+
+The image now manages volumes and configuration in a better fashion,
+thanks to that we achieve an image that is closer to the original one, but
+gets the plugins that we want and the configuration that we want for
+integration with DD.
+
+You can now define `BBB_HOST` and `BBB_API_SECRET` as variables in dd.conf,
+which are used to configure the corresponding plugin on Nextcloud.
+
+You can also define a list of custom plugins to enable/disable in Nextcloud
+with the dd.conf variables: `NEXTCLOUD_PLUGINS_ENABLE`,
+`NEXTCLOUD_PLUGINS_DISABLE`. See `dd.conf.sample` for more information.
+
+If upgrading from previous versions, you probably will want to check the
+permissions assigned to the `user_saml` plugin directory.
+You can also force its reinstallation with proper permissions with:
+
+    # Usually SRC_FOLDER in dd.conf is /opt/DD/src
+    rm -rf "${SRC_FOLDER:-/opt/DD/src}/nextcloud/custom_apps/user_saml/"
+    # Restart the NC container (only if previous command runs after upgrade)
+    # docker-compose restart dd-apps-nextcloud-app
+
+
+Upgrade from a commit that includes Nextcloud major version 24 (see previous
+UPGRADE messages) with:
+
+    # Upgrade to NC version 24.0.10 (latest 24 minor on 2023-03-14)
+    # Note this commit already includes the reworked image
+    ./dd-ctl update 010a04bf37d75b39cf24bcc2b80c81023e037f78
+    # Upgrade to NC version 25.0.5  (latest 25 minor on 2023-03-31)
+    ./dd-ctl update a4f51d102396ebc0883882dfbcebd9e08f60a7b8
+
 ### 2023-02 - Nextcloud 24.0.10
 
 Update version to 24.0.10