Upgrade from Stash 2.11 and lower to 3.9 - 4.11 does not set correct service user label for migrated access keys

In Stash 3.9, a label column was added to the sta_service_user table, which is used to distinguish different types of service users.

When the column was added, the SSH upgrade task that creates service users for access keys (created before 2.10), was not updated to also set the appropriate label for these service users. As a result, the service users that are created as part of the upgrade task as created with the default 'bot' label instead of the 'access-key' label.

The migrated access keys work fine, but cannot be deleted. See BSERV-8388.

This issue covers fixing the upgrade task to correctly set the label. This will ensure that upgrades from 3.8 and lower to 4.12 and higher will not have the problem described in BSERV-8388.

It does not correct the label on incorrectly upgraded sta_service_user as for instances that have migrated from 3.8 (or lower) to 3.9 - 4.11. That will be fixed as part of BSERV-8388.