This commit addresses several issues:

1. The overwrite of `_recompute_completion` was not properly filtering
the partners that had actually completed the course. meaning that
passing through this function could add a course/slide.channel as an
employee skill iven if they did not complete it. Now, we only act upon
employees that have actually finished the course.

2. The function would add the same skill over and over again, assuming
that we could only pass through it once but it is actually called every
time we publish or archive any slide of a course since 9920f20e.
This can lead to a bit of bloat on an employee resume  (See task
attachments). Now, we try to make the function idempotent and only add a
resumé line only once.

3. The addition of a resume line could not be achieved and would raise
an ACL when the current user was not an HR Officer (group `hr_user`).
Since it can be called by any eLearning(`slides`) manager, a sudo
privilege is necessary.

Related Task: 2830016

closes odoo/odoo#93555

Signed-off-by: Kevin Baptiste <kba@odoo.com>

The license is missing in most enterprise manifest so
the decision was taken to make it explicit in all cases.
When not defined, a warning will be triggered starting from
14.0 when falling back on the default LGPL-3.

closes odoo/odoo#74231

Related: odoo/enterprise#19850
Related: odoo/design-themes#43
Signed-off-by: Xavier Dollé (xdo) <xdo@odoo.com>