New dev/task to initialise DataObjects for existing datasets

docs/en/migrating-from-single-language.md

@@ -4,12 +4,14 @@ In case you want to add fluent to an existing site to add multi language functio
 
 ## Install fluent
 
-use composer to install fluent, see [installation](installation.md)
+Use composer to install fluent, see [installation](installation.md)
 
 ## Configure fluent
-* add locales
 
-You can either do this in the backend, or for the first setup you can utitlise `default_records` to add the locales to the db. 
+* Add locales
+
+You can either do this in the backend, or for the first setup you can utitlise `default_records` to add the locales to
+the db.
 A fluent.yml might look like:
 
 ```
@@ -33,32 +35,121 @@ TractorCow\Fluent\Model\Locale:
 
 When you run `dev/build?flush` again, this adds the records to the database if the locales table is still empty.
 
-## Publish available pages in your default locale
+## Populating initial localised content for existing Pages and DataObjects in your default locale
 
-Now your site is broken, cause no pages have been published and added as translated page in your default locale. 
-You can either publish all pages manually or use [publishall](https://docs.silverstripe.org/en/4/developer_guides/debugging/url_variable_tools/#building-and-publishing-urls) to publish all pages in bulk.
-If you run `/admin/pages/publishall` in your browser  your site will be fixed again and you can start adding translated content.  
+Now your site is broken because nothing has been published and added as translated data in your default locale. You can
+either manually localise all DataObjects & Pages manually or use one of the automation options below.
 
 ### Automated tools for localisation
 
-`InitialPageLocalisation` dev task can be used to either only localise or localise & publish your pages.
-This dev task can be run either via CLI or queued as a job if Queued jobs module is installed.
-
-Localise only example
-
-```
-dev/tasks/initial-page-localisation-task
-```
-
-Localise & publish example
-
-```
-dev/tasks/initial-page-localisation-task publish=1
-```
-
-Localisation in batches can be done by using the `limit` option.
-Example below will localise & publish five pages on each run.
-
-```
-dev/tasks/initial-page-localisation-task publish=1&limit=5
-```
+#### From the CMS (SiteTree only)
+
+Use Silverstripe's
+built-in [publishall](https://docs.silverstripe.org/en/4/developer_guides/debugging/url_variable_tools/#building-and-publishing-urls)
+tool to publish all Pages in bulk.
+Run `/admin/pages/publishall` in your browser and your site will be fixed again and you can start adding translated
+content.
+
+_This method will work with Pages only (not localised DataObjects)._
+
+#### Commandline or Queued Jobs (SiteTree and DataObjects)
+
+The `InitialPageLocalisation` and `InitialDataObjectLocalisationTask` dev tasks may be used to localise and, optionally,
+publish your `Versioned` data (including Pages) from the commandline or queued as a job (if the Queued Jobs module is installed).
+
+`InitialPageLocalisation` - localise all `SiteTree` objects (Pages)
+
+`InitialDataObjectLocalisationTask` - localise all Fluent-enabled DataObjects (excluding `SiteTree`)
+
+1. Example: Localise all Pages (default, without publishing)
+
+   ```
+   dev/tasks/initial-page-localisation-task
+   ```
+
+2. Example: Localise & publish all Pages
+
+    ```
+    dev/tasks/initial-page-localisation-task publish=1
+    ```
+
+3. Example: Localising Pages in batches can be done by using the `limit` option. 
+   This will localise & publish five pages on each run.
+
+    ```
+    dev/tasks/initial-page-localisation-task publish=1&limit=5
+    ```
+
+4. Example: All the same functionality is available for localising all DataObjects, including `Versioned` and non-Versioned classes
+
+    ```
+    dev/tasks/initial-dataobject-localisation-task
+    ```
+    or
+
+    ```
+    dev/tasks/initial-dataobject-localisation-task publish=1&limit=5
+    ```
+
+#### Customize your own initialisation dev task
+
+Perhaps you want to be more selective in how you initialise your localised content.
+The `InitialDataObjectLocalisationTask` class can be easily extended to either list exactly which classes you want to
+initially localise, or you can exclude specific classes from initialisation.
+
+1. **Initialise specific classes:** The following example will create a task which localises **_ONLY_** `BlogPost`
+pages, `Testimonial` objects, _and their subclasses (if any)_.
+
+    ```php
+    class CustomLocalisationTask extends InitialDataObjectLocalisationTask
+    {
+        /**
+         * @var string
+         */
+        private static $segment = 'custom-localisation-initialisation-task';
+
+        /**
+         * @var string
+         */
+        protected $title = 'Custom localisation initialisation';
+
+        /**
+         * @var string[]
+         */
+        protected array $include_only_classes = [
+            \SilverStripe\Blog\Model\BlogPost::class,
+            \AcmeCo\Model\Testimonial::class
+        ];
+
+    }
+    ```
+
+2. **Initialise all DataObjects but exclude some:** The following example will create a task which localises **_ALL_**
+DataObjects **_except_** `BlogPost` pages, `Testimonial` objects, _and their subclasses (if any)_.
+
+    ```php
+    class CustomLocalisationTask extends InitialDataObjectLocalisationTask
+    {
+        /**
+         * @var string
+         */
+        private static $segment = 'custom-localisation-initialisation-task';
+
+        /**
+         * @var string
+         */
+        protected $title = 'Custom localisation initialisation';
+
+        /**
+         * @var string[]
+         */
+        protected array $exclude_classes = [
+            \SilverStripe\Blog\Model\BlogPost::class,
+            \AcmeCo\Model\Testimonial::class
+        ];
+
+    }
+    ```
+
+3. **One or the other:** You may specify `$include_only_classes` OR `$exclude_classes` - not both.
+If `$include_only_classes` is not an empty array, `$exclude_classes` will be ignored.