Required by T409: Migrate InformAzionI's stuff from proprietary services to nextCloud. Increased priority.

Apparently, upgrading from 10.3.0 to nextCloud is not officially supported.

So we followed these official guides:

https://help.nextcloud.com/t/migration-from-owncloud-10-3-0-to-nextcloud/62618

https://docs.nextcloud.com/server/19/admin_manual/maintenance/manual_upgrade.html

alter table oc_persistent_locks
	drop foreign key FK_F0C3D55BC901C6FF,
	drop owner_account_id;
alter table oc_persistent_locks drop foreign key FK_F0C3D55B93CB796C, drop file_id;

Then:

1. installed Calendar and Contacts from website again.
2. reinstalled Contacts application
3. tried to update to Nextcloud 13.0.12 but at the end of the process:

This version of Nextcloud is not compatible with > PHP 7.2.

4. commented out hardcoded version limitation from `lib/versioncheck.php
5. updated to NextCloud 14.0.14 successfully
6. reinstalled Contacts and Calendar applications
7. updated to NextCloud 15.0.12
8. followed instructions from the settings page:

sudo -u www-data php occ db:add-missing-indices
sudo -u www-data php occ db:convert-filecache-bigint

9. updated to NextCloud 16.0.11 successfully
10. reinstall Contacts and Calendar applications
11. followed instructions from the settings page:

sudo -u www-data php occ db:add-missing-indices
sudo -u www-data php occ db:convert-filecache-bigint

12. updated to NextCloud 17.0.9 successfully
13. a wild red toast with [Object Object] as message appeared!

14. updated to NextCloud 18.0.9 successfully

Oh shit the update frontend page now feels less shitty, giant blue box, awesome.

Still red toast with [Object Object] as message.

15. followed instructions from the website:

sudo -u www-data php occ db:add-missing-indices

16. reinstall Calendar application and also Contact application (even if this latest one was working)
17. updated Contacts application (boh)

Still with the red toast `[Object Object]'. Boh.

18. re-enable Calendar application

19. Now nextCloud ask for your password to enable an application. Awesome.

20. updated to NextCloud 19.0.3 successfully
21. followed instructions on the website:

sudo -u www-data php occ db:add-missing-indices
sudo -u www-data php occ db:add-missing-columns

Everything works, but the website suggests php-bcmath and php-gmp.

AWESOME IT WORKS