Search sponsorship_hash case insensitive in check_sponsor endpoint
CHANGELOG:
### Changed
- [#811](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/811) Search sponsorship_hash case insensitive in check_sponsor endpoint
Related card: https://trello.com/c/xptmycnQ/1276-apadrinaments-comprovaci%C3%B3-de-codi-no-sensible-a-maj%C3%BAscules
Edited by Pelayo García