adding documentation to change nextcloud data path

[Alexis-IMBERT]

close : #674

Problem

• Trouble finding a proper way to change the location of Nextcloud's data folder

Solution

• Adding the command to change the data path of Nextcloud in admin documentation (with french translation)

PR Status

• Code finished and ready to be reviewed/tested
• The fix/enhancement were manually tested (if applicable)

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[Alexis-IMBERT]

!testme

[Alexis-IMBERT]

Hi!
I read this doc https://yunohost.org/fr/packaging_apps_resources#data-dir

When the mirgation is effective ?

I reinstalled my server but when I did the command the folder was not created, and when I create a new files in nextcloud, the file is created on the first folder

[alexAubin]

Related to https://github.com/YunoHost/doc/blob/master/pages/04.applications/10.docs/nextcloud/app_nextcloud.md#ii-migrate-nextcloud-data-to-a-larger-partition which is actually supposed to be removed and/or migrated to the app's ADMIN.md as a consequence of YunoHost/doc#2417

This old piece of doc actually seems to recommend a savage cp + edition of the config.php + the data dir setting

The symlink solution seems better but I don't remember why exactly but this ultimately also causes issues later on (maybe with backups if i remember correctly)

There is also https://yunohost.org/en/administer/tutorials/external_storage which to me sounds like the most reliable solution and uses bind mounts

Ideally we should harmonize all this because this is quite a reccuring question/issue and currently there's no way to move apps data in a simple yet long-term robust way