Specify SiteAccess for translations data migrations (#2247)

---------

Co-authored-by: Adrien Dupuis <[email protected]>
Co-authored-by: Magdalena Dziadosz <[email protected]>

Author: adriendupuis

docs/content_management/data_migration/exporting_data.md

@@ -14,7 +14,7 @@ or in [a custom folder that you configure](managing_migrations.md#migration-fold
 You can later use this file to import the data.
 
 ``` bash
-php bin/console ibexa:migrations:generate --type=content --mode=create
+php bin/console ibexa:migrations:generate --type=content --mode=create --siteaccess=admin
 ```
 
 This generates a file containing all Content items.
@@ -134,6 +134,12 @@ Note that you should test your migrations. See [Importing data](importing_data.m
 
     Migration command can be executed with database rollback at the end with the `--dry-run` option.
 
+!!! caution
+
+    The `--siteaccess` option usage can be relevant for a multi-language repository.
+    You must export with a SiteAccess that supports all languages, or the migration skips translations in non-supported languages.
+    It is recommended to use the SiteAccess from the Back Office of the targeted repository.
+
 ## type
 
 The mandatory `--type` option defines the type of Repository data to export.

docs/content_management/data_migration/importing_data.md

@@ -15,13 +15,17 @@ and specify the file name within this folder as parameter.
 If you don't specify the file, all files within this directory are used.
 
 ``` bash
-php bin/console ibexa:migrations:migrate --file=my_data_export.yaml
+php bin/console ibexa:migrations:migrate --file=my_data_export.yaml --siteaccess=admin
 ```
 
 Migrations store execution metadata in the `ibexa_migrations` database table.
 This allows incremental upgrades:
 the `ibexa:migrations:migrate` command ignores files that it had previously executed.
 
+Notice that `--siteaccess` option usage is important when several languages are used.
+You must import with a SiteAccess that supports all languages, or the migration skips translations in non-supported languages.
+It's recommended to use the SiteAccess from the Back Office of the targeted repository.
+
 ## Migration step
 
 A data migration step is a single operation in data migration process