Because we were backing up to trash documents in the wrong order (in the example
from the test, portal_categories/test_category/removed_container/removed_document
first and then portal_categories/test_category/removed_container), first the
document was backed-up and some intermediate trash folders were created to
keep the hierarchy. Then when backing up the container, there was an error like:

    BadRequest: The id "removed_container" is invalid - it is already in use.

Similar error happens when upgrading erp5_configurator_standard, it was failing with:

    BadRequest: The id "officejs_sdk_workflow" is invalid - it is already in use.

The fix is to backup in reverse order, to back up first the containers and then
the document in containers.