Migration have long been only accessible thanks to a symlink from
`odoo.base.maintenance` to our private migration repository. Thank to
the change of bbb1a8f it is now possible to give a load the
migrations scripts from a path given in options.
The `initialize_sys_path` function has been updated to hooks the new
paths or the legacy symlink and to provide aliases to the previous
import logic to ensure backward compatibility.
`odoo.upgrades` (`community/odoo/upgrades`) is a new namespace that hook
all `--upgrades-paths` directories or the
`community/odoo/base/maintenance/migrations` symlink if none is previded.
`odoo.addons.base.maintenance.migrations` has been made an alias to
`odoo.upgrades`.
The `odoo.upgrades` is the desired method for accessing migrations
scripts and should be used by all new scripts.
closesodoo/odoo#44117
Task: 2178274
X-original-commit: d963cc05acd882729c4eb5ab940dae2a2197e55a
Signed-off-by: Raphael Collet (rco) <rco@openerp.com>