Once a user posts a review, they are able to edit this single review and not create any new ones. However if the user had multiple tabs open of the same course, then they can still access the "Add a review" functionality. This fix enforces the single review per user per course policy. Task-3721958 closes odoo/odoo#156411 X-original-commit: 61a95ad41e0b0c72554a491c555ddd33d8588566 Signed-off-by: Stéphane Debauche (std) <std@odoo.com> Signed-off-by: Bram Van Gaal (brvg) <brvg@odoo.com>