Add offer attribute to catalog products
CHANGELOG:
### CHANGED
- [#905](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/905) Add offer attribute to catalog products
Related card: https://trello.com/c/YHM4rofM/1423-new-attribute-api-productcatalog
Edited by César López Ramírez